Protective layers for electrochemical cells

ABSTRACT

Articles and methods including layers for protection of electrodes in electrochemical cells are provided. As described herein, a layer, such as a protective layer for an electrode, may comprise a plurality of particles (e.g., crystalline inorganic particles, amorphous inorganic particles). In some embodiments, at least a portion of the plurality of particles (e.g., inorganic particles) are fused to one another. For instance, in some embodiments, the layer may be formed by aerosol deposition or another suitable process that involves subjecting the particles to a relatively high velocity such that fusion of particles occurs during deposition. In some embodiments, the layer (e.g., the layer comprising a plurality of particles) is an ion-conducting layer.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/160,191, filed May 20, 2016, which claims priority under 35 U.S.C.§119(e) to U.S. Provisional Patent Application Ser. No. 62/164,200,filed May 20, 2015, each of which is incorporated herein by reference inits entirety for all purposes.

FIELD

Articles and methods including ion-conductive layers, e.g., forprotection of electrodes in electrochemical cells, are provided.

BACKGROUND

One of the factors that decreases cycle life in lithium- (or otheralkali metal- or alkali earth metal-) based batteries is the consumptionof electrolyte during cycling of the battery due to reaction of metalliclithium present in the electrodes with the electrolyte. In order tominimize, or substantially prevent, this reaction and consequentlyincrease the cycle life of the cell, it is desirable to isolate themetallic lithium from the electrolyte. This often times involves the useof a lithium ion conductive material layer coated on the surface of themetallic lithium. This material allows lithium ions to diffuse to andfrom the metallic lithium surface while excluding the electrolyte fromcontacting the lithium surface, therefore preventing any side reactionsbetween lithium and the electrolyte. Although certain protectivestructures have been fabricated, improvements in the protectivestructures for lithium and other alkali metal electrodes would bebeneficial and would have application in a number of different fieldsinvolving the use of such batteries and electrodes.

SUMMARY

Articles and methods including ion-conductive layers for protection ofelectrodes in electrochemical cells, are provided. In certainembodiments, electrode structures and/or methods for making electrodestructures including an anode comprising lithium metal or a lithiummetal alloy and an ion-conductive layer including a plurality ofparticles (e.g., fused inorganic particles) described herein areprovided. The subject matter disclosed herein involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In one set of embodiments, a series of articles are provided. In oneembodiment, an article for use in an electrochemical cell comprises afirst layer and a second layer disposed on the first layer, wherein thesecond layer comprises a plurality of particles, and wherein the secondlayer is substantially non-porous. The plurality of particles comprisean ionically conductive material. At least a portion of the plurality ofparticles are at least partially embedded within the first layer. Atleast a portion of the plurality of particles are fused to one another.The second layer has an ionic conductivity between about 10⁻⁶ S/cm andabout 10⁻² S/cm. The second layer has an average thickness between about0.5 microns and about 50 microns.

In another embodiment, an article for use in an electrochemical cellcomprises a first layer and a second layer disposed on the first layer,wherein the second layer comprises an ionically conductive material anda non-ionically conductive material. At least a portion of the ionicallyconductive material is crystalline. The ionically conductive material ispresent in the second layer in an amount greater than 85 wt % of thesecond layer. The second layer has an ionic conductivity between about10⁻⁶ S/cm and about 10⁻² S/cm. The second layer has an average thicknessbetween about 0.5 microns and about 50 microns.

In another set of embodiments, electrochemical cells are provided. Inone embodiment, an electrochemical cell comprises a first layer and asecond layer disposed on the first layer, wherein the second layercomprises a plurality of particles having a particle size of greaterthan 0.5 microns, wherein the plurality of particles comprise anionically conductive material. The second layer has an ionicconductivity between about 10⁻⁶ S/cm and about 10⁻² S/cm. The secondlayer has an average thickness between about 0.5 microns and about 50microns. The electrochemical cell also includes a liquid electrolyte.The second layer is substantially impermeable to the liquid electrolyte.

In another set of embodiments, a series of methods are provided. In oneembodiment, a method of forming an article for use in an electrochemicalcell is provided. The method comprises exposing a first layer comprisinga first material to a plurality of particles having a velocity of atleast 200 m/s, wherein the particles comprise a second materialdifferent from the first material. The method also involves embedding atleast a portion of the particles in the first layer, and forming asecond layer comprising the second material, wherein the second layerhas an ionic conductivity between about 10⁻⁶ S/cm and about 10⁻² S/cm.

In another embodiment, a method of forming an article for use in anelectrochemical cell comprises exposing a first layer comprising a firstmaterial to a plurality of particles having a velocity sufficient tocause fusion of at least some of the particles, wherein the particlescomprise a second material. The method involves embedding at least aportion of the particles in the first layer, and forming a second layercomprising the second material, wherein the second layer has an ionicconductivity between about 10⁻⁶ S/cm and about 10⁻² S/cm.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1A is a schematic representation of an ion-conductive layerdeposited on an underlying layer, according to one set of embodiments;

FIG. 1B is another schematic representation of an ion-conductive layerdeposited on an underlying layer, according to one set of embodiments;

FIG. 1C is a schematic representation of an ion-conductive layerdeposited on an underlying layer and an electrolyte layer, according toone set of embodiments;

FIGS. 2A-B are a schematic representation of a method for manufacturingan electrode structure, according to one set of embodiments;

FIG. 3A shows a cross-sectional view SEM image of an ion-conductivelayer, according to one set of embodiments;

FIG. 3B shows another cross-sectional view SEM image of theion-conductive layer in FIG. 3A, according to one set of embodiments;

FIGS. 3C-3D show top-down SEM views of the ion-conductive layer in FIGS.3A-3B, according to one set of embodiments;

FIGS. 4A-4C show cross-sectional view SEM images of anotherion-conductive layer, according to one set of embodiments;

FIGS. 5A-5C show top-down SEM views of yet another ion-conductive layer,according to one set of embodiments;

FIG. 5D shows a cross-sectional view SEM image of the ion-conductivelayer in

FIGS. 5A-5C, according to one set of embodiments; and

FIGS. 6A-6B show top-down SEM views of an ion-conductive layer,according to one set of embodiments.

DETAILED DESCRIPTION

Articles and methods including layers for protection of electrodes inelectrochemical cells are provided. As described herein, a layer, suchas a protective layer for an electrode, may comprise a plurality ofparticles (e.g., crystalline inorganic particles, amorphous inorganicparticles). In some embodiments, at least a portion of the plurality ofparticles (e.g., inorganic particles) are fused to one another. Forinstance, in some embodiments, the layer may be formed by aerosoldeposition or another suitable process that involves subjecting theparticles to a relatively high velocity such that fusion of particlesoccurs during deposition. In some embodiments, the layer (e.g., thelayer comprising a plurality of particles) is an ion-conducting layer.In some cases, the layer (e.g., the ion-conducting layer) comprises arelatively low amount of polymer (e.g., less than or equal to about 20vol % polymer versus total volume fraction of the layer). At least aportion of the plurality of particles may be embedded within anotherlayer (e.g., a substrate, such as an electrode). In certain embodiments,the plurality of particles are formed of a first material (e.g., aninorganic material), and the layer may comprise a second material (e.g.,an inorganic material, a polymeric material) different from the firstmaterial. When used as a protective layer, the protective layer may besubstantially impermeable to a liquid electrolyte.

Advantageously, an ion-conductive layer described herein may maintainthe bulk properties of the materials used to form the layer (e.g.,crystallinity, ion-conductivity), may exhibit increased flexibility,and/or may permit the incorporation of materials (e.g., ceramics) thatwould not be generally feasible under traditional vacuum depositionmethods.

The disclosed ion-conductive layers may be incorporated into anelectrochemical cell. such as a lithium-based electrochemical cell(e.g., a lithium-sulfur electrochemical cell, a lithium-ionelectrochemical cell). Although several of the embodiments describedherein involve use of such a layer as a protective layer for anelectrode, it should be appreciated that the layer may be used as anyother appropriate component within an electrochemical cell.

In some embodiments in which the electrochemical cell is alithium-sulfur electrochemical cell, the incorporation of ion-conductivelayers as described herein into electrochemical cells may prevent orreduce the occurrence of chemical reactions between polysulfides (e.g.,found in electrolytes comprising polysulfides) and an electroactivematerial of an anode (e.g., an anode comprising lithium, such asmetallic lithium). The use of ion-conductive layers as described hereinmay offer several advantages over certain traditional protective layers,including increasing utilization of sulfur within an electrochemicalcell, reduction or elimination of the shuttle affect, and/or reductionor elimination of electrolyte depletion. Ion-conductive layers and/orcomposite structures comprising a plurality of particles, as describedin more detail herein, may, in some cases, selectively conduct lithiumcations. In some embodiments, the ion-conductive layers and/or compositestructures comprising a plurality of particles are not conductivetowards certain ions, such as polysulfide anions, and/or may function asa barrier (e.g., protective structure) for electrolytes (e.g., liquidelectrolytes).

Moreover, ion-conductive layers as described herein may offer additionaladvantages over certain traditional protective layers includingincreased flexibility, mechanical stability, chemical stability, and/orion conductivity, e.g., between a lithium anode and an electrolyte. Forexample, certain existing protective layers (e.g., including certainceramic-based ion conductive layers), such as certain protective layersin the form of thin, homogeneous films, may be very thin, brittle,easily cracked during handling or use, porous, and/or contain defectswhich, as a result, do not have sufficient barrier properties to preventelectrolytes and/or polysulfides from diffusing and/or reacting with anelectroactive material of an anode (e.g., an anode comprising lithium).By contrast, an ion-conductive layer comprising a plurality of fusedparticles may maintain the bulk properties of the materials used to formthe layer, exhibit increased flexibility, permit the incorporation ofmaterials (e.g., ceramics) that would not be generally feasible undertraditional vacuum deposition methods, and/or decrease manufacturingcost.

In one particular embodiment, flexibility of the ion-conductive layermay be achieved by including a polymer in the ion-conductive layer(e.g., with the plurality of particles). The polymer may benon-ionically conductive, in some cases, such that the layer does notswell in an electrolyte used with the electrochemical cell. In some suchembodiments, ionic conduction is maintained across the layer because acontinuous pathway (e.g., from a first surface of the ion-conductivelayer to a second surface of the ion-conductive layer) is present (e.g.,due to fusion of at least a portion of the particles within the layer).In addition, because the particles within the layer may have relativelyhigh ion conductivity, the ion conductivity of the layers describedherein may be comparable to those of certain existing protective layers.

The disclosed ion-conductive layers may be incorporated intoelectrochemical cells, for example, primary batteries or secondarybatteries, which can be charged and discharged numerous times. In someembodiments, the materials, systems, and methods described herein can beused in association with lithium batteries (e.g., lithium-sulfurbatteries, lithium-ion batteries). The electrochemical cells describedherein may be employed in various applications, for example, making oroperating cars, computers, personal digital assistants, mobiletelephones, watches, camcorders, digital cameras, thermometers,calculators, laptop BIOS, communication equipment or remote car locks.It should be appreciated that while much of the description hereinrelates to lithium-sulfur and/or lithium-ion batteries, theion-conductive layers described herein may be applied to otherlithium-based batteries, as well as other alkali metal-based batteries.

Turning now to the figures, the various embodiments of the currentdisclosure are described in more detail below. It should be understoodthat while certain layers depicted in the figures are disposed directlyon one another, other intermediate layers may also be present betweenthe depicted layers in certain embodiments. Accordingly, as used herein,when a layer is referred to as being “disposed on”, “deposited on”, or“on” another layer, it can either be directly disposed on, depositedonto, or on the layer, or an intervening layer may also be present. Incontrast, a layer that is “directly disposed on”, “in contact with”,“directly deposited on”, or “directly on” another layer indicates thatno intervening layer is present.

FIG. 1A depicts one embodiment of an electrode structure 10. Theelectrode structure includes a first layer 20 (e.g., an electroactivelayer) and a second layer 30 (e.g., an ion-conductive layer) depositedon the first layer at first surface 30′. As described herein, secondlayer 30 may be used as a protective layer to protect the underlyinglayer (e.g., from reaction with an electrolyte, or species within theelectrolyte). Second layer 30 may comprise, in some cases, a pluralityof particles. The plurality of particles may be of a single type, or ofmore than one type, as described in more detail below. In someembodiments, the first layer comprises a first material (e.g., anelectroactive material, a material used to form a separator, substrate,or other component) and the second layer comprises a second materialdifferent from the first material (e.g., a plurality of particlescomprising an inorganic material different than the material used toform the first layer).

In some embodiments, the plurality of particles (e.g., inorganicparticles) are fused. For example, as illustrated in FIG. 1B, electrodestructure 10 comprises first layer 20 (e.g., an electroactive layer orother layer described herein), second layer 30 (e.g., an ion-conductivelayer), and a plurality of particles 40. In some such embodiments, atleast a portion of the plurality of particles 40 are fused as shownillustratively in the figure. In certain embodiments, the plurality ofparticles (e.g., fused inorganic particles) are embedded in the firstlayer. For instance, as described in more detail below, the second layermay be formed at least in part by subjecting the first layer toparticles traveling at a certain velocity such that the particlesimpinge upon the first layer upon contact, and/or fuse with one anotherupon collision. As shown in this illustrative embodiment, second layer30 has first surface 30′, which may be adjacent the first layer 20. Theplurality of particles (e.g., the plurality of fused particles) may, insome cases, contact and/or be embedded in at least a portion of thefirst layer 20 at first surface 30′.

In some embodiments, the average largest cross-sectional dimension ofthe particles (e.g., prior to being fused or absent any fusion) may be,for example, less than or equal to 20 microns, less than or equal toabout 10 microns, less than or equal to about 5 microns, less or equalto about 2 microns, less than or equal to about 1 micron, or less thanor equal to about 0.75 microns. In some embodiments, the average largestcross-sectional dimension of the plurality of particles (e.g., prior tobeing fused or absent any fusion) may be greater than or equal to about0.5 microns, greater than or equal to about 0.75 microns, greater thanor equal to about 1 micron, greater than or equal to about 1.5 microns,greater than or equal to about 2 microns, greater than or equal to about3 microns, greater than or equal to about 5 microns, greater than orequal to about 10 microns, or greater than or equal to about 15 microns.Combinations of the above-referenced ranges are also possible (e.g., alargest cross-sectional dimension of less than about 20 microns andgreater than about 0.5 microns, a largest cross-sectional dimension ofless than about 15 microns and greater than about 1 micron). In someembodiments in which more than one particle type is included in a layer,each particle type may have a value of particle size in one or more ofthe above-referenced ranges.

In some embodiments, the average largest cross-sectional dimension ofthe particles (e.g., after being deposited on a surface) may be, forexample, less than or equal to about 10 microns, less than or equal toabout 5 microns, less or equal to about 2 microns, less than or equal toabout 1 micron, less than or equal to about 0.75 microns, less than orequal to about 0.5 microns, less than or equal to about 0.2 microns,less than or equal to about 0.1 microns. In some embodiments, theaverage largest cross-sectional dimension of the plurality of particles(e.g., after being deposited on a surface) may be greater than or equalto about 0.01 microns, greater than or equal to about 0.1 microns,greater than or equal to about 0.5 microns, greater than or equal toabout 0.75 microns, greater than or equal to about 1 micron, greaterthan or equal to about 1.5 microns, greater than or equal to about 2microns, greater than or equal to about 3 microns, greater than or equalto about 5 microns. Combinations of the above-referenced ranges are alsopossible (e.g., a largest cross-sectional dimension of less than about10 microns and greater than about 0.1 microns, a largest cross-sectionaldimension of less than about 5 microns and greater than about 0.01micron). In some embodiments in which more than one particle type isincluded in a layer, each particle type may have a value of particlesize in one or more of the above-referenced ranges.

As described above, in some embodiments at least a portion of theplurality of particles in a layer may be fused. The terms “fuse” and“fused” (and “fusion”) are given their typical meaning in the art andgenerally refers to the physical joining of two or more objects (e.g.,particles) such that they form a single object. For example, in somecases, the volume occupied by a single particle (e.g., the entire volumewithin the outer surface of the particle) prior to fusion issubstantially equal to half the volume occupied by two fused particles.Those skilled in the art would understand that the terms “fuse”,“fused”, and “fusion” do not refer to particles that simply contact oneanother at one or more surfaces, but particles wherein at least aportion of the original surface of each individual particle can nolonger be discerned from the other particle.

In some cases, the particles are fused such that at least a portion ofthe plurality of particles form a continuous pathway across the secondlayer (e.g., between a first surface of the second layer and a secondsurface of the second layer). A continuous pathway may include, forexample, an ionically-conductive pathway from a first surface to asecond, opposing surface of the layer in which there are substantiallyno gaps, breakages, or discontinuities in the pathway. Whereas fusedparticles across a layer may form a continuous pathway, a pathwayincluding packed, unfused particles would have gaps or discontinuitiesbetween the particles that would not render the pathway continuous. Incertain embodiments, the layer includes a plurality of such continuouspathways across the layer. In some embodiments, at least 10 vol %, atleast 30 vol %, at least 50 vol %, or at least 70 vol % of the secondlayer comprises one or more continuous pathways comprising fusedparticles (e.g., which may comprise an ionically conductive material).In certain embodiments, less than or equal to about 100 vol %, less thanor equal to about 90 vol %, less than or equal to about 70 vol %, lessthan or equal to about 50 vol %, less than or equal to about 30 vol %,less than or equal to about 10 vol %, or less than or equal to about 5vol % of the second layer comprises one or more continuous pathwayscomprising fused particles. Combinations of the above-referenced rangesare also possible (e.g., at least about 10 vol % and less than or equalto about 100 vol %). In some cases, 100 vol % of the second layercomprises one or more continuous pathways comprising fused particles.That is to say, in some embodiments, the second layer consistsessentially of fused particles (e.g., the second layer comprisessubstantially no unfused particles). In other embodiments, substantiallyall of the particles are unfused.

Those skilled in the art would be capable of selecting suitable methodsfor determining if the particles are fused including, for example,performing Confocal Raman Microscopy (CRM). CRM may be used to determinethe percentage of fused areas within a layer described herein. Forinstance, in some embodiments the fused areas may be less crystalline(more amorphous) compared to the unfused areas (e.g., particles) withinthe layer, and may provide different Raman characteristic spectral bandsthan those of the unfused areas. In certain embodiments the fused areasmay be amorphous and the unfused areas (e.g., particles) within thelayer may be crystalline. Crystalline and amorphous areas may have peaksat the same/similar wavelengths, while amorphous peaks may bebroader/less intense than those of crystalline areas. In some instances,the unfused areas may include spectral bands substantially similar tothe spectral bands of the bulk particles prior to formation of the layer(the bulk spectrum). For example, an unfused area may include peaks atthe same or similar wavelengths and having a similar area under the peak(integrated signal) as the peaks within the spectral bands of theparticles prior to formation of the layer. An unfused area may have, forinstance, an integrated signal (area under the peak) for the largestpeak (the peak having the largest integrated signal) in the spectrumthat may be, e.g., within at least 70%, at least 75%, at least 80%, atleast 85%, at least 90%, at least 95%, or at least 97% of value of theintegrated signal for the corresponding largest peak of the bulkspectrum. By contrast, the fused areas may include spectral bandsdifferent from (e.g., peaks at the same or similar wavelengths buthaving a substantially different/lower integrated signal than) thespectral bands of the particles prior to formation of the layer. A fusedarea may have, for instance, an integrated signal (area under the peak)for the largest peak (the peak having the largest integrated signal) inthe spectrum that may be, e.g., less than 50%, less than 60%, less than70%, less than 75%, less than 80%, less than 85%, less than 90%, lessthan 95%, or less than 97% of value of the integrated signal for thecorresponding largest peak of the bulk spectrum. In some embodiments,2-dimensional or 3-dimensional mapping of CRM may be used to determinethe percentage of fused areas in the layer (e.g., the percentage ofarea, within a minimum cross-sectional area, having an integrated signalfor the largest peak of the spectrum that differs from that for theparticles prior to formation of the layer, as described above). Theminimum cross-sectional area of the layer used for such an analysis maybe, for example, at least 600 μm², at least 900 μm², at least 1000 μm²,at least 2000 μm², at least 3000 μm², at least 5000 μm², at least 7000μm², or at least 10,000 μm², and the intervals of measurement (spatialresolution) within the area may be, for example, 1 μm² or less, 2 μm² orless, 4 μm² or less, 6 μm² or less, or 9 μm² or less. (If a3-dimensional image is obtained, the minimum volume of the layer usedfor such an analysis may be, for example, at least 600 μm³, at least 900μm³, at least 1000 μm³, at least 2000 μm³, at least 3000 μm³, at least5000 μm³, at least 7000 μm³, or at least 10,000 μm³, and the intervalsof measurement (spatial resolution) within the volume may be, forexample, 1 μm³ or less, 4 μm³ or less, 8 μm³ or less, 16 μm³ or less, 27μm³ or less, or 64 μm³ or less,) An average of at least 3, 5, or 7images may be used to determine percentage of fused area for aparticular sample.

In other embodiments, the presence of fused particles may be determinedby determining the conductivity of a layer. For instance, a layercomprising fused particles may have an average conductivity greater thanan average conductivity of a layer in which the particles are not fused,all other factors being equal. An average of at least 3, 5, or 7measurements may be used to determine the conductivity for a particularsample.

The plurality of particles may be deposited and/or fused using anysuitable method. In some embodiments, a method may involve forming anion-conductive layer (e.g., a second layer) adjacent to or on a portionof a first layer (e.g., an electroactive material such as an anodecomprising lithium, a cathode (e.g., comprising sulfur or other suitablesubstrate as described herein)). In one set of embodiments, theplurality of particles are deposited and/or fused via an aerosoldeposition process. Aerosol deposition processes are known in the artand generally comprise depositing (e.g., spraying) particles (e.g.,inorganic particles, polymeric particles) at a relatively high velocityon a surface. For example, in some embodiments, the plurality ofparticles are deposited on the first layer (e.g., the electroactivematerial layer) at a relative high velocity such that at least a portionof the plurality of particles fuse (e.g., forming the second layer onthe first layer). The velocity required for particle fusion may dependon factors such as the material composition of the particles, the sizeof the particles, the Young's elastic modulus of the particles, and/orthe yield strength of the particles or material forming the particles.

As described herein, in some embodiments, the particles are deposited ata velocity sufficient to cause fusion of at least some of the particles.It should be appreciated, however, that in some embodiments, theparticles are deposited at a velocity such that at least some of theparticles are not fused. In certain embodiments, the velocity of theparticles is at least about 150 m/s, at least about 200 m/s, at leastabout 300 m/s, at least about 400 m/s, or at least about 500 m/s, atleast about 600 m/s, at least about 800 m/s, at least about 1000 m/s, orat least about 1500 m/s. In some embodiments, the velocity is less thanor equal to about 2000 m/s, less than or equal to about 1500 m/s, lessthan or equal to about 1000 m/s, less than or equal to about 800 m/s,600 m/s, less than or equal to about 500 m/s, less than or equal toabout 400 m/s, less than or equal to about 300 m/s, or less than orequal to about 200 m/s. Combinations of the above-referenced ranges arealso possible (e.g., between about 150 m/s and about 2000 m/s, betweenabout 150 m/s and about 600 m/s, between about 200 m/s and about 500m/s, between about 200 m/s and about 400 m/s, between about 500 m/s andabout 2000 m/s). Other velocities are also possible. In some embodimentsin which more than one particle type is included in a layer, eachparticle type may be deposited at a velocity in one or more of theabove-referenced ranges.

In some embodiments, the deposition method comprises spraying theparticles (e.g., via aerosol deposition) on the surface of a first layerby pressurizing a carrier gas with the particles. In some embodiments,the pressure of the carrier gas is at least about 5 psi, at least about10 psi, at least about 20 psi, at least about 50 psi, at least about 90psi, at least about 100 psi, at least about 150 psi, at least about 200psi, at least about 250 psi, or at least about 300 psi. In certainembodiments, the pressure of the carrier gas is less than or equal toabout 350 psi, less than or equal to about 300 psi, less than or equalto about 250 psi, less than or equal to about 200 psi, less than orequal to about 150 psi, less than or equal to about 100 psi, less thanor equal to about 90 psi, less than or equal to about 50 psi, less thanor equal to about 20 psi, or less than or equal to about 10 psi.Combinations of the above-referenced ranges are also possible (e.g.,between about 5 psi and about 350 psi). Other ranges are also possibleand those skilled in the art would be capable of selecting the pressureof the carrier gas based upon the teachings of this specification. Forexample, in some embodiments, the pressure of the carrier gas is suchthat the velocity of the particles deposited on the first layer issufficient to fuse at least some of the particles to one another.

In some embodiments, the carrier gas (e.g., the carrier gas with theparticles) is heated prior to deposition. In some embodiments, thetemperature of the carrier gas is at least about 20° C., at least about25° C., at least about 30° C., at least about 50° C., at least about 75°C., at least about 100° C., at least about 150° C., at least about 200°C., at least about 300° C., or at least about 400° C. In certainembodiments, the temperature of the carrier gas is less than or equal toabout 500° C., is less than or equal to about 400° C., is less than orequal to about 300° C., is less than or equal to about 200° C., is lessthan or equal to about 150° C., is less than or equal to about 100° C.,is less than or equal to about 75° C., is less than or equal to about50° C., is less than or equal to about 30° C. or less than or equal toabout 20° C. Combinations of the above-referenced ranges are alsopossible (e.g., between about 20° C. and about 500° C.). Other rangesare also possible. In certain embodiments, the particles are depositedunder a vacuum environment.

For example, in some embodiments, the particles may be deposited on thefirst layer in a container in which vacuum is applied to the container(e.g., to remove atmospheric resistance to particle flow, to permit highvelocity of the particles, and/or to remove contaminants). In certainembodiments, the vacuum pressure within the container is at least about0.5 mTorr, at least about 1 mTorr, at least about 2 mTorr, at leastabout 5 mTorr, at least about 10 mTorr, at least about 20 mTorr, or atleast about 50 mTorr. In certain embodiments, the vacuum pressure withinthe container is less than or equal to about 100 mTorr, less than orequal to about 50 mTorr, less than or equal to about 20 mTorr, less thanor equal to about 10 mTorr, less than or equal to about 5 mTorr, lessthan or equal to about 2 mTorr, or less than or equal to about 1 mTorr.Combinations of the above-referenced ranges are also possible (e.g.,between about 0.5 mTorr and about 100 mTorr). Other ranges are alsopossible.

As described herein, in some embodiments a layer (e.g., a second layersuch as an ion-conductive layer) is formed by a method involving aerosoldeposition of particles. Aerosol deposition, as described herein,generally results in the collision and/or elastic deformation of atleast some of the plurality of particles. In some embodiments, aerosoldeposition can be carried out under conditions (e.g., using a velocity)sufficient to cause fusion of at least some of the plurality ofparticles to at least another portion of the plurality of particles.

In some embodiments, a process described herein for forming a secondlayer can be carried out such that the bulk properties of the precursormaterials (e.g., particles) are maintained in the resulting layer (e.g.,crystallinity, ion-conductivity). In some cases, the use of aerosoldeposition permits the deposition of particles formed of certainmaterials (e.g., ceramics) not feasible using other depositiontechniques (e.g., vacuum deposition). For example, vacuum deposition(e.g., such as sputtering, e-beam evaporation) typically involvesrelatively high temperatures that would cause some ceramic materials tolose their bulk properties (e.g., crystallinity and/or ion conductivity)upon deposition. In other embodiments, vacuum deposition of certainmaterials leads to cracking of the resulting layer because suchmaterials may have desirable mechanical properties in the crystallinestate which are lost during vacuum deposition (e.g., as amorphous films)resulting in crack formation and/or mechanical stresses formed in thelayer (e.g., as a result of strength and/or thermal characteristicmismatch between the substrate and the layer). In certain cases,tempering of the material may not be possible after vacuum depositionfor at least the aforementioned reasons. Since aerosol deposition can becarried out at relatively lower temperatures, e.g., compared to certainvacuum deposition techniques, certain materials (e.g., crystallinematerials) that are typically incompatible with forming an-ionconductive layer/protective layer can now be used.

In one exemplary method, and referring to FIG. 2A, forming a secondlayer (e.g., an ion-conductive layer) may involve providing a firstlayer 120 (e.g., an electroactive layer or other layer described herein)as a substrate for the formation of the second layer. Particles 140(e.g., inorganic particles) may be deposited by any suitable method(e.g., aerosol deposition). Referring now to FIG. 2B, particles 140 maybe deposited (as indicated by the arrow) on first layer 120. Thedeposition of the particles may cause the particles to be at leastpartially embedded within the first layer. In certain embodiments, theparticles are deposited at a sufficient velocity such that at least someof the particles come into direct contact with and/or are at leastpartially embedded within the first layer. In some embodiments, theparticles are deposited at a sufficient velocity such that at least someof the plurality of particles are at least partially embedded within thefirst layer and at least some of the particles are fused (FIG. 2B).

In some embodiments, at least a portion of the plurality of particles ofa layer, or at least a portion of the surfaces of the plurality ofparticles, are in contact (e.g., direct contact) with a first layer(e.g., an electroactive layer or other layer described herein). Thisconfiguration can allow transport of ions (e.g., metal ions, such aslithium ions) directly from the particles to the first layer. In somecases, at least a portion of the plurality of particles is embeddedwithin the first layer. For example, in some cases, at least about 0.1vol % of the particles of a layer (e.g., a second layer) is embeddedwithin the first layer. In some embodiments, at least about 1 vol %, atleast about 5 vol %, or at least about 10 vol %, or at least 20 vol % ofthe particles is embedded within the first layer. In certainembodiments, less than or equal to about 25 vol %, less than or equal toabout 20 vol %, less than or equal to about 15 vol %, or less than orequal to about 10 vol % of the particles is embedded within the firstlayer. Combinations of the above-referenced ranges are also possible(e.g., between about 0.1 vol % and about 25 vol %). Other ranges arealso possible. Methods for determining the volume percentage ofparticles within a layer are known within the art and may include, insome embodiments, dissecting an ion-conductive layer and imaging with,for example, a scanning electron microscope.

Certain conventional electrodes and/or electrochemical cells are made toinclude an electroactive layer and/or an ion-conductive layer that is assmooth as possible (e.g., prior to cycling), where such smoothness wasthought to help increase cycle life (e.g., by reducing pitting or otherdeterious effects). In one particular set of embodiments describedherein, at least a portion of the particles used to form anion-conductive layer (e.g., a protective layer) are embedded in anelectroactive material layer and result in a particular roughness of theelectroactive material layer and/or ion-conductive layer. Theelectroactive material layer and/or ion-conductive layer may have acertain value or range of values of mean peak to valley roughness asdescribed herein (e.g., prior to cycling). In some embodiments, suchroughness does not substantially negatively affect cycle life.

As described herein, in some embodiments, the second layer is anion-conductive layer. The ion-conductive layer may include a firstsurface (e.g., in contact with a first layer, such as an electroactivelayer) and a second surface opposing the first surface. In certainembodiments, a surface (e.g., a second surface) of the ion-conductivelayer is in contact with an additional layer of an electrode orelectrochemical cell (e.g., an optional electrolyte layer 50 in FIG.1C). In some embodiments, at least some of the particles (e.g., fusedparticles) comprises a first portion in direct contact with theelectroactive layer at the first surface of the ion-conductive layer,and a second portion at the second surface of the ion-conductive layer.For example, the second portion of at least some of the fused particlesat the second surface may be in direct contact with an electrolytematerial (e.g., an electrolyte layer).

As described above, layers comprising a plurality of particles may serveas a protective layer. In some embodiments, the ion-conductive layer issubstantially impermeable to a liquid electrolyte (e.g., a liquidelectrolyte to be used in an electrochemical cell including theprotective layer). For example, in some embodiments, the ion-conductivelayer absorbs less than or equal to about 10 wt %, less than or equal toabout 5 wt %, less than or equal to about 1 wt %, less than or equal toabout 0.5 wt %, or less than or equal to about 0.1 wt % of a liquidelectrolyte versus the total weight of the ion-conductive layer. Incertain embodiments, the ion-conductive layer absorbs at least about0.01 wt %, at least about, 0.1 wt %, at least about 0.5 wt %, at leastabout 1 wt %, or at least about 5 wt % of a liquid electrolyte versusthe total weight of the ion-conductive layer. Combinations of theabove-referenced ranges are also possible (e.g., between about 0.01 wt %and about 5 wt %, between about 0.01 wt % and about 0.5 wt %). Thoseskilled in the art would be capable of selecting suitable methods fordetermining the liquid electrolyte absorbed by the ion-conductive layerincluding, for example, measuring the difference in weight of theion-conductive layer after absorbing the liquid electrolyte (e.g., afterexposing the layer to the electrolyte for 1 hour at ambient temperatureand pressure) versus the weight of the ion-conductive layer beforeabsorbing the liquid electrolyte.

In some embodiments, the layer comprising a plurality of particles(e.g., fused particles) is substantially non-swellable. For example, thelayer (e.g., the ion-conductive layer) may comprise a polymer that issubstantially non-swellable in a liquid electrolyte to be used in anelectrochemical cell including the protective layer. In some suchembodiments, the polymer is substantially non-ionically conductive(e.g., the polymer may have an ion-conductivity of less than about 10⁻⁸S/cm. Polymers including non-ionically conductive polymers are describedin more detail, below.

The particles of an ion-conductive layer and/or the resultingion-conductive layer described herein can be formed of a variety oftypes of materials. In certain embodiments, the material from which theparticles are formed may be selected to allow ions (e.g.,electrochemically active ions, such as lithium ions) to pass through thematerial but to substantially impede electrons from passing across thematerial. By “substantially impedes”, in this context, it is meant thatin this embodiment the material allows lithium ion flux at least tentimes greater than electron passage. The particles may comprise, forexample, an ion-conductive material (e.g., to facilitate the transfer ofions between materials on either side of the ion-conductive layer).Advantageously, such particles may be capable of conducting specificcations (e.g., lithium cations) while not conducting certain anions(e.g., polysulfide anions) and/or may be capable of acting as a barrierto an electrolyte and/or a polysulfide species for the electroactivelayer.

In some embodiments, the particles and/or an ion-conductive layerdescribed herein comprise and/or are formed of an inorganic material. Incertain embodiments, the inorganic material comprises a ceramic material(e.g., glasses, glassy-ceramic materials). Non-limiting examples ofsuitable ceramic materials include oxides (e.g., aluminum oxide, siliconoxide, lithium oxide), nitrides, and/or oxynitrides of aluminum,silicon, zinc, tin, vanadium, zirconium, magnesium, indium, and alloysthereof, Li_(x)MP_(y)S_(z) (where x, y, and z are integers, e.g.,integers less than 20; and where M=Sn, Ge, or Si) such as LiMP₂S₁₂(e.g., where M=Sn, Ge, Si) and LiSiPS, garnets, crystalline or glasssulfides, phosphates, perovskites, anti-perovskites, other ionconductive inorganic materials and mixtures thereof. Li_(x)MP_(y)S_(z)particles can be formed, for example, using raw components Li₂S, SiS₂and P₂S₅ (or alternatively Li₂S, Si, S and P₂S₅), for example.

In some embodiments, the particles of an ion-conductive layer, and/or anion-conductive layer itself, may comprise a material including one ormore of lithium nitrides, lithium silicates, lithium borates, lithiumaluminates, lithium phosphates, lithium phosphorus oxynitrides, lithiumsilicosulfides, lithium germanosulfides, lithium oxides (e.g., Li₂O,LiO, LiO₂, LiRO₂, where R is a rare earth metal), lithium lanthanumoxides, lithium titanium oxides, lithium borosulfides, lithiumaluminosulfides, and lithium phosphosulfides, oxy-sulfides (e.g.,lithium oxy-sulfides) and combinations thereof. In some embodiments, theplurality of particles may comprise Al₂O₃, ZrO₂, SiO₂, CeO₂, and/orAl₂TiO₅. In a particular embodiment, the plurality of particles maycomprise Li—Al—Ti—PO₄ (LATP). The selection of the material (e.g.,ceramic) will be dependent on a number of factors including, but notlimited to, the properties of electrolyte and the anode and cathode usedin the cell.

In some embodiments, the particles of an ion-conductive layer, and/or anion-conductive layer itself, may comprise a polymeric material (e.g., anon-ionically conductive polymeric material and/or an ion-conductivepolymeric material). Polymeric materials suitable for use in anion-conductive layer (or as particles for forming an ion-conductivelayer) are described in more detail below.

In some embodiments, the particles of an ion-conductive layer, and/or anion-conductive layer itself, are/is substantially amorphous. In certainembodiments, the particles and/or an ion-conductive layer describedherein are/is substantially crystalline. In some cases, the particlesand/or an ion-conductive layer described herein may be semi-crystalline.For example, in some embodiments, the particles and/or an ion-conductivelayer described herein may be at least about 1% crystalline, at leastabout 2% crystalline, at least about 5% crystalline, at least about 10%crystalline, at least about 25% crystalline, at least about 50%crystalline, at least about 75% crystalline, at least about 80%crystalline, at least about 90% crystalline, at least about 95%crystalline, at least about 98% crystalline, at least about 99%crystalline. In certain embodiments, the particles and/or anion-conductive layer described herein may be 100% crystalline. In someembodiments, the particles and/or an ion-conductive layer describedherein may be less than or equal to about 99.9% crystalline, less thanor equal to about 99.5% crystalline, less than or equal to about 99%crystalline, less than or equal to about 98% crystalline, less than orequal to about 95% crystalline, less than or equal to about 90%crystalline, less than or equal to about 80% crystalline, less than orequal to about 75% crystalline, less than or equal to about 50%crystalline, less than or equal to about 25% crystalline, less than orequal to about 10% crystalline, less than or equal to about 5%crystalline, or less than or equal to about 2% crystalline. Combinationsof the above referenced ranges are also possible (e.g., between about 1%crystalline and 100% crystalline, between about 1% crystalline and about99.9% crystalline). Those skilled in the art would be capable ofselecting suitable methods for determining percent crystallinityincluding, for example, x-ray diffraction spectra of the particlesand/or ion-conductive layer.

The plurality of particles may include more than one type of particles.For example, a first portion of the plurality of particles may comprisea first type of inorganic material and a second portion of the pluralityof particles may comprising a second type of inorganic material. Inanother example, a first portion of the plurality of particles maycomprise an inorganic material and a second portion of the plurality ofparticles may comprise a polymeric material. In yet another example, afirst portion of the plurality of particles may comprise a first type ofpolymeric material and a second portion of the plurality of particlesmay comprise a second type of polymeric material. In some embodiments,the plurality of particles comprise more than one, more than two, ormore than three types of particles (e.g., inorganic, polymeric, orcombinations thereof). For instance, a layer may include at least 2, atleast 3, at least 4 types of particles, wherein each of the particletypes are different.

In some embodiments, the particles of an ion-conductive layer may beselected to have a desirable ion conductivity. For example, in certainembodiments, the particles may be conductive to ions of theelectroactive material (e.g. lithium). In some cases, the particles mayhave an average ion conductivity (e.g., lithium ion conductivity) of atleast about 10⁻⁶ S/cm. In certain embodiments, the average ionconductivity (e.g., metal ion, such as lithium ion conductivity) of theparticles within the ion-conductive layer is at least about 10⁻⁶ S/cm,at least about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about, orat least about 10⁻³ S/cm. In some embodiments, the average ionconductivity of the particles is less than about 10⁻² S/cm, less thanabout 10⁻³ S/cm, or less than about 10⁻⁴ S/cm. Combinations of theabove-reference ranges are also possible (e.g., an ion conductivitybetween about 10⁻² S/cm and about 10⁻⁶ S/cm, between about 10⁻³S/cm andabout 10⁻⁵S/cm). Other ion conductivity is are also possible.Conductivity may be measured at room temperature (e.g., 25 degreesCelsius).

In some embodiments, the average ion conductivity of the particles canbe determined before the particles are incorporated into theion-conductive layer. The average ionic conductivity can be measured bypressing the particles between two copper cylinders at a pressure of upto 3 tons/cm². In certain embodiments, the average ion conductivity(i.e., the inverse of the average resistivity) can be measured at 500kg/cm² increments using a conductivity bridge (i.e., an impedancemeasuring circuit) operating at 1 kHz. In some such embodiments, thepressure is increased until changes in average ion conductivity are nolonger observed in the sample.

In certain embodiments, the particles may have an electronicconductivity of less than about 10⁻¹⁰ S/cm. For example, in someembodiments, the electronic conductivity of the particles is less thanor equal to about 10⁻¹¹ S/cm, less than or equal to about 10⁻¹² S/cm,less than or equal to about 10⁻¹³ S/cm, less than or equal to about10⁻¹⁴ S/cm, less than or equal to about 10⁻¹⁵ S/cm, less than or equalto about 10⁻¹⁷ S/cm, or less than or equal to about 10⁻¹⁹ S/cm. Othervalues and ranges of electronic conductivity are also possible.

In certain embodiments, the particles (e.g., fused particles) of theion-conductive layer are substantially non-porous. For instance, in someembodiments, the particles do not have any substantial “dead space”where undesirable species such as air can be trapped within theparticles, since trapping of such species can reduce the ionconductivity of the particles. In some cases, an average porosity of theparticles may be less than about 10 vol %, less than about 5 vol %, lessthan about 2 vol %, less than about 1 vol %, or less than about 0.1 vol%. In some embodiments, the average porosity of the particles may bebetween about 0.01 vol % and about 0.1 vol %, or between about 0.1 vol %and about 2 vol %.

Average porosity can be measured, for example, using a mercuryporosimeter. Briefly, average porosity can be determined by measuringthe external pressure required to force a liquid (e.g., mercury) into apore (e.g., against the opposing force of surface tension between theliquid and the pore). Those skilled in the art would be capable ofselecting an appropriate range of external pressures based upon theparticles selected.

It may be advantageous for the particles to comprise a material that ischemically stable when in contact with one or more layers of theelectrochemical cell. Generally, particles are chemically stable if thematerial forming the particles does not react chemically (e.g., form abyproduct) with a component of one or more materials that may come indirect contact with the particles. For example, in certain embodiments,the particles are chemically stable when in contact with theelectroactive material, when in contact with the polymeric material,when in contact with an electrolyte material, and/or when in contactwith a polysulfide.

In some embodiments, the weight percentage of the particles (e.g., fusedparticles) in the ion-conductive layer is between about 80 wt % andabout 99.9 wt %. That is to say, in some embodiments, the ion-conductivelayer includes between about 80 wt % and about 99.9 wt % of an ionicallyconductive material. In certain embodiments, the ion-conductive layercomprises particles (or ionically conductive material) in an amountgreater than or equal to about 80 wt %, greater than or equal to about85 wt %, greater than or equal to about 90 wt %, greater than or equalto about 95 wt %, greater than or equal to about 97 wt %, greater thanor equal to about 98 wt %, or greater than or equal to about 99 wt % ofthe total composition of the ion-conductive layer. In some embodiments,the weight percentage of the particles (or ionically conductivematerial) in the ion-conductive layer is less than about 99.9 wt %, lessthan or equal to about 99.5 wt %, less than about 99 wt %, less thanabout 98 wt %, less than about 97 wt %, less than about 95 wt %, lessthan about 90 wt %, or less than about 85 wt % of the total compositionof the ion-conductive layer. Combinations of the above-reference rangesare also possible (e.g., between about 80 wt % and about 99.9 wt %,between about 80 wt % and about 95 wt %, between about 80 wt % and about90 wt %). Other ranges are also possible. Methods for determining theweight percentage of particles within a layer are known within the artand may include, in some embodiments, weighing the particles and thepolymer before the formation of the ion-conductive layer.

As described herein, aerosol deposition of particles may be used to forman ion-conductive layer on a substrate as described herein. In certainembodiments, the difference between the hardness of the particles andthe hardness of the substrate on which the particles are deposited maybe less than or equal to 200%, less than or equal to 100%, less than orequal to 80%, less than or equal to 60%, less than or equal to 40%, lessthan or equal to 20%, less than or equal to 10%, or less than or equalto 5%. In some embodiments, the difference in hardness may be at least0.01%, at least 0.1%, at least 1%, at least 5%, at least 10%, or atleast 50%. Combinations of the above-referenced ranges are alsopossible. The difference may be calculated by subtracting the smallervalue of hardness from the larger value of hardness, dividing by thelarger value of hardness, and multiplying by 100. Those skilled in theart would be capable of selecting suitable methods for determininghardness of the materials described herein, including, for example,nanoindentation.

In some embodiments, the ion-conductive layer comprises an additionalmaterial. For example, in some cases, the ion-conductive layer comprisesa non-ionically conductive material. In certain embodiments, theion-conductive layer comprises an additional conductive material (e.g.,an ionically conductive material). The additional material may be inparticulate form or non-particulate form.

In some embodiments, the additional material is an inorganic material.Inorganic materials are described above, in regards to the plurality ofparticles, and may be suitable for use as an additional material.

In some embodiments, an ion-conductive layer may include a polymericmaterial. The polymeric material may be present in the ion-conductivelayer in the spaces between the particles (e.g., fused particles)forming the layer. For instance, the layer may include a composite ofparticles (e.g., fused particles) and regions of polymeric material.

In some embodiments, the polymeric material is deposited (e.g., aerosoldeposited) on a first layer. In certain embodiments, particles (e.g.,polymer particles) comprising the polymeric material is deposited on thefirst layer. The polymer material may be deposited substantiallysimultaneously with deposition of the inorganic material (e.g., theparticles and the polymeric material may be mixed prior to deposition,or may be introduced from different sources onto the same substrate).

In other embodiments, the polymeric material may be deposited on thefirst layer prior to deposition of the particles of inorganic material.For instance, after forming a first layer comprising a polymericmaterial (which may be deposited by aerosol deposition, or by any othersuitable method for forming a polymeric layer, such as a coating method)the inorganic particles may be deposited on and/or into the polymericmaterial. In certain embodiments, the inorganic particles may bedeposited after and onto/into the polymer material such that at least aportion of the inorganic particles fuse.

In some embodiments involving depositing inorganic (e.g., ceramic)particles onto a polymeric layer, a gradient in the density of theinorganic material/particles across the thickness of the layer may beformed. For instance, in one method, a polymeric layer is positioned ona first layer (e.g., a substrate). The polymeric material may be in anysuitable form (e.g., a gel, a solid). Then, inorganic particles may bedeposited onto the polymeric layer (e.g., by aerosol deposition). Theresulting structure may be a composite of the inorganic particles andthe polymeric material, with the density of inorganic materialincreasing across at least a portion (or substantially all of) thethickness of the resulting structure from the first layer to the outersurface of the structure. Such a structure may be formed, in someembodiments, by increasing the velocity of the inorganic particlesgradually throughout deposition. In some instances, the depositionoccurs such that at least a portion of the inorganic particles fuse. Forinstance, the particles/inorganic material at the outer surface of theresulting structure may be substantially fused, while theparticles/inorganic material adjacent the first surface may remainsubstantially unfused, partially fused, or fused to a lesser extentcompared to that at the outer surface. In other embodiments, the reversegradient can be formed.

Methods and conditions (e.g., velocity, pressures, etc.) for depositingmaterials are described in detail herein.

Any suitable polymeric material can be included in an ion-conductivelayer. In some embodiments, the polymeric material may include orconsist essentially of one or more polymeric materials. The polymericmaterial may, in some embodiments, be a monomer, a mixture ofcopolymers, block copolymers, or a combination of two or more polymersthat are in an interpenetrating network or semi-interpenetratingnetwork. In alternative embodiments, the polymeric material may comprisea filler and/or solid additive. The filler and/or solid additive may addstrength, flexibility, and/or improved adhesion properties to thepolymer. In some embodiments, the polymer may comprise a plasticizer orother additives, including solid phase change materials. Addition ofplasticizers may increase flexibility of the polymer and improvethixotropic properties. Addition of solid phase change materials mayresult in addition of materials that melt at elevated temperatures andthereby act as a heat sink and prevent thermal runaway.

In some embodiments, the polymeric material may be selected to beflexible. Nano-hardness studies may be conducted to measure creep and/orhardness and thereby assess the flexibility and/or brittleness of apolymeric material. In certain cases, the polymeric material may beselected to be thermally stable above 100° C., 150° C., 200° C., 250°C., 300° C., 350° C., or 400° C. Thermal stability may be assessed bydifferential scanning calorimetry (DSC). Non-limiting examples ofpolymeric materials that may exhibit thermal stability at elevatedtemperatures include polysiloxanes, polycyanurates, andpolyisocyanurates.

The polymeric material may, in certain cases, be selected to besubstantially inert to the electrolyte solution and/or to Li polysulfideattack. A means of determining the stability of a polymeric material inan electrolyte solution includes exposing a small sample of thepolymeric material to vapors of an electrolyte solvent, or to theelectrolyte solvent itself. Examples of polymeric materials that may bestable in an electrolyte solution include, but are not limited to,polyurethanes and polysiloxanes. Additional tests that may be conductedon polymeric materials to examine various characteristics includeFourier transform infrared spectroscopy (FTIR) to confirm that apolymeric material is cured or cross-linked, scanning electronmicroscopy with energy dispersive x-ray spectroscopy (SEM-EDS) todetermine whether a polymeric material has cracks. Such test and othertests can also be used to determine whether an ion-conductive layercomprises discrete layers, interpenetrating networks, orsemi-interpenetrating networks. Profilometry can be used to assess howrough the surface of a polymeric material is.

Other classes of polymeric materials that may be suitable for use in anion-conductive layer (e.g., as particles to be fused during formation ofthe ion-conductive layer) include, but are not limited to, polyamines(e.g., poly(ethylene imine) and polypropylene imine (PPI)); polyamides(e.g., polyamide (Nylon), poly(e-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), polyimides (e.g., polyimide,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton));vinyl polymers (e.g., polyacrylamides, poly(acrylates),poly(methacrylates), poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(vinyl acetate), poly (vinyl alcohol),poly(vinyl chloride), poly(vinyl fluoride), poly(2-vinyl pyridine),vinyl polymer, polychlorotrifluoro ethylene, andpoly(isohexylcynaoacrylate)); polyacetals; polyolefins (e.g.,poly(butene-1), poly(n-pentene-2), polyethylene, polypropylene,polytetrafluoroethylene); polyesters (e.g., polycarbonate, polybutyleneterephthalate, polyhydroxybutyrate); polyethers (poly(ethylene oxide)(PEO), poly(propylene oxide) (PPO), poly(tetramethylene oxide) (PTMO));vinylidene polymers (e.g., polyisobutylene, poly(methyl styrene),poly(methylmethacrylate) (PMMA), poly(vinylidene chloride), andpoly(vinylidene fluoride)); polyaramides (e.g., poly(imino-1,3-phenyleneiminoisophthaloyl) and poly(imino-1,4-phenylene iminoterephthaloyl));polyheteroaromatic compounds (e.g., polybenzimidazole (PBI),polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT));polyheterocyclic compounds (e.g., polypyrrole); polyurethanes; phenolicpolymers (e.g., phenol-formaldehyde); polyalkynes (e.g., polyacetylene);polydienes (e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene);polysiloxanes (e.g., poly(dimethylsiloxane) (PDMS),poly(diethylsiloxane) (PDES), polydiphenylsiloxane (PDPS), andpolymethylphenylsiloxane (PMPS)); and inorganic polymers (e.g.,polyphosphazene, polyphosphonate, polysilanes, polysilazanes). In someembodiments, the polymeric material may be selected from the groupconsisting of polyvinyl alcohol, polyisobutylene, epoxy, polyethylene,polypropylene, polytetrafluoroethylene, and combinations thereof. Themechanical and electronic properties (e.g., conductivity, resistivity)of these polymers are known.

Accordingly, those of ordinary skill in the art can choose suitablepolymeric materials based on their mechanical and/or electronicproperties (e.g., ionic and/or electronic conductivity), and/or canmodify such polymeric materials to be ionically conducting (e.g.,conductive towards single ions) and/or electronically non-conductingbased on knowledge in the art, in combination with the descriptionherein. As described herein, in some embodiments the polymeric materialis substantially non-ionically conductive. However, in other embodimentsin which it is desirable for the polymeric material to be ionicallyconductive (e.g., particles comprising such ionically conductivepolymeric materials), the polymeric materials listed above and hereinmay further comprise salts, for example, lithium salts (e.g., LiSCN,LiBr, LiI, LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity. Saltsmay be added to the material in a range of, e.g., 0 to 50 mol %. Incertain embodiments, salts are included in at least 5 mol %, at least 10mol %, at least 20 mol %, at least 30 mol %, at least 40 mol %, or atleast 50 mol % of the material. In certain embodiments, additional saltsare less than or equal to 50 mol %, less than or equal to 40 mol %, lessthan or equal to 30 mol %, less than or equal to 20 mol %, or less thanor equal to 10 mol % of the material. Combinations of the above-notedranges are also possible. Other values of mol % are also possible.

In certain embodiments, the average ionic conductivity of the polymericmaterial may be less than or equal to about 10⁻³ S/cm, less than orequal to about 10⁴ S/cm, less than or equal to about 10⁻⁵ S/cm, lessthan or equal to about 10⁻⁶ S/cm, or less than or equal to about 10⁻⁷S/cm. In some embodiments, the average ionic conductivity of thepolymeric material of an ion-conductive layer is at least about 10⁻⁸S/cm, at least about 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, at least about10⁻⁵ S/cm, at least about 10⁴ S/cm, or at least about 10⁻³ S/cm.Combinations of the above-referenced ranges are also possible (e.g., anaverage ionic conductivity in the electrolyte of at least about 10⁻⁸S/cm and less than or equal to about 10⁻⁶ S/cm). Conductivity may bemeasured at room temperature (e.g., 25 degrees Celsius).

In some embodiments, the polymeric material may be substantiallynon-ionically conductive and substantially non-electrically conductive.For example, non-electrically conductive materials (e.g., electricallyinsulating materials) such as those described herein can be used. Inother embodiments, the polymeric material may be ionically conductivebut substantially non-electrically conductive. Examples of suchpolymeric materials include non-electrically conductive materials (e.g.,electrically insulating materials) that are doped with lithium salts,such as acrylate, polyethylene oxide, silicones, and polyvinylchlorides.

In some embodiments, the polymeric material included in a composite issubstantially non-swellable in an electrolyte solvent to be used in anelectrochemical cell including such an ion-conductive layer. Forinstance, the polymeric material may experience a volume change of lessthan 10%, less than 8%, less than 6%, less than 5%, less than 4%, lessthan 2%, or less than 1% when in contact with an electrolyte solvent(including any salts or additives present) to be used in anelectrochemical cell including such an ion-conductive layer for at least24 hours. In some embodiments, the polymeric material (e.g., the gelcomprising the polymeric material) may increase in volume (i.e. swell)in the presence of the liquid electrolyte by at least about 0.01 vol %,at least about 0.1 vol %, at least about 0.2 vol %, at least about 0.5vol %, at least about 1 vol %, or at least about 2 vol %. Combinationsof the above referenced ranges are also possible (e.g., between about0.01 vol % and about 5 vol %). Simple screening tests of such polymerscan be conducted by placing pieces of polymer in the electrolyte solvent(including any salts or additives present) and measuring the weight orvolume change of the polymer pieces before and after a 24 hour period,and determining the percentage change in volume relative to the volumebefore placement in the solvent.

It may be advantageous, in some embodiments, for the polymeric materialto comprise or be formed of a material that is chemically stable when incontact with one or more layers of the electrochemical cell (e.g., anelectrolyte layer). The polymeric material may be chemically stable if,for example, the material does not react chemically (e.g., form abyproduct) with a component of one or more additional layers of theelectrochemical cell in direct contact with the polymeric material. Forexample, in certain embodiments, the polymeric material is chemicallystable when in contact with the electroactive material, when in contactwith an electrolyte material, and/or when in contact with a polysulfide.In certain embodiments, the polymeric material may form a reactionproduct with the components of the electrode for electrochemical cell(e.g., an electroactive material, an electrolyte material (e.g., aspecies within the electrolyte), and/or a polysulfide); however, in suchembodiments, the reaction product does not interfere with the functionof a layer including the polymeric material (e.g., the layer remainsionically conductive).

In certain embodiments, the polymeric material may be substantiallynon-cross-linked. However, in other embodiments, the polymeric materialis cross-linked. In some such embodiments, the polymeric material may becross-linked with a portion of the plurality of particles. For example,in some embodiments, a portion of the plurality of particles may becoated with a cross-linking polymer (e.g., bound to the surface of aportion of the plurality of particles). Cross-linking can be achievedby, for example, adding cross-linker to a polymer and performing across-linking reaction, e.g., by thermal or photochemical curing, e.g.by irradiation with such as UV/vis irradiation, by γ-irradiation,electron beams (e-beams) or by heating (thermal cross-linking). Examplesof cross-linkers may include ones selected from molecules with two ormore carbon-carbon double bonds, e.g., ones with two or more vinylgroups. Particularly useful cross-linkers are selected fromdi(meth)acrylates of diols such as glycol, propylene glycol, diethyleneglycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, triethyleneglycol, tetrapropylene glycol, cyclopentadiene dimer, 1,3-divinylbenzene, and 1,4-divinyl benzene. Some suitable cross-linkers maycomprise two or more epoxy groups in the molecule, such as, for example,bis-phenol F, bis-phenol A, 1,4-butanediol diglycidyl ether, glycerolpropoxylate triglycidyl ether, and the like.

In some embodiments, the polymeric material may be in the form of a gel.In some embodiments, the polymeric material forms a polymer gel whenexposed to a liquid electrolyte. In certain embodiments, the polymericmaterial may swell in the presence of a liquid electrolyte. For example,in some embodiments, the polymeric material (e.g., the gel comprisingthe polymeric material) may increase in volume (i.e. swell) in thepresence of the liquid electrolyte by at least about 20 vol %, at leastabout 30 vol %, at least about 40 vol %, at least about 50 vol %, atleast about 60 vol %, at least about 70 vol %, at least about 80 vol %,or at least about 90 vol %. In certain embodiments, the polymericmaterial may increase in volume (i.e. swell) in the presence of a liquidelectrolyte by less than or equal to about 200 vol %, less than or equalto about 100 vol %, less than or equal to about 80 vol %, less than orequal to about 60 vol %, less than or equal to about 40 vol %, or lessthan or equal to about 20 vol %. Combinations of the above referencedranges are also possible (e.g., between about 50 vol % and about 100 vol%). Simple screening tests of such polymer gels can be conducted byplacing pieces of polymer gel in the electrolyte solvent (including anysalts or additives present) and measuring the weight or volume change ofthe gel pieces before and after a 24 hour period, and determining thepercentage change in volume relative to the volume before placement inthe solvent.

In some embodiments, the additional material (e.g., the polymericmaterial) is present in the ion-conductive layer in an amount of atleast about 5 wt %, at least about 10 wt %, at least about 20 wt %, orat least about 25 wt %. In certain embodiments, the additional materialis present in the ion-conductive layer is less than or equal to about 30wt %, less than or equal to about 25 wt %, less than or equal to about20 wt %, less than or equal to about 15 wt %, or less than or equal toabout 10 wt %. Combinations of the above referenced ranges are alsopossible (e.g., between about 5 wt % and about 30 wt %). Other rangesare also possible. In some cases, the ion-conductive layer comprisessubstantially no additional material.

As described above, in some embodiments, flexibility of theion-conductive layer may be achieved by including a polymer in theion-conductive layer.

In some cases, flexibility may be characterized by, for example,determining the critical radius of curvature (e.g., by a bending testand scanning electron microscopy and/or profilometry measurementsconducted at a particular bend radius), nano-hardness tests, and/or AFMindentation (e.g., nanoindentation).

In some embodiments, the ion-conductive layer may have a particularcritical radius of curvature. For example, a first ion-conductive layercomprising a plurality of particles and an additional material may havean overall thickness, a total amount of particles (e.g., fusedparticles), and a total amount of additional material. A second,comparative ion-conductive layer (e.g., comprising the plurality ofparticles) may have the same or similar overall thickness, thesame/similar total amount of inorganic material, but substantially noadditional material, or the same/similar total amount of additionalmaterial, but the additional material comprising an inorganic material.The first ion-conductive layer may have a critical radius of curvaturelarger than the critical radius of curvature of the secondion-conductive layer, e.g., by at least a factor of about 2, at least afactor of about 10, at least a factor of about 20, at least a factor ofabout 50, or at least a factor of about 100, in some embodiments up to afactor of 1000, or up to a factor of 500. A critical radius of curvaturefor the first ion-conductive layer that is larger than the criticalradius of curvature for the second ion-conductive layer may indicatethat the first composite is more flexible than the second composite. Thecritical radius of curvature may be determined for each ion-conductivelayer according to any method known in the art. For example, thecritical radius of curvature may be determined using a bending test.Such a test may involve obtaining a sample (e.g. a sample havingdimensions of 5 cm×2.5 cm). The geometric center of the sample isdetermined by optical profilometry. The edges of the sample are movedtogether, causing the sample to be bent into the shape of an arc. Forexample, for a sample having a length of 5 cm, the edges of the samplemay be moved to distances ranging from about 4.5 cm (e.g., a slightchange, or relatively small radius of curvature) to about 2.5 cm (e.g.,a severe change, or relatively large radius of curvature). At differentdistances, the radius of curvature of the sample may be measured, andthe presence or absence of fractures may be determined by opticalprofilometry at the geometric center. The critical radius of curvatureis the minimum radius of curvature at which fracture begins to takeplace at the geometric center of the sample. In some embodiments, theplurality of particles comprise an ionically conductive material havinga particular Young's elastic modulus. In some embodiments, the Young'selastic modulus of the plurality of particles is at least about 0.1 GPa,at least about 0.5 GPa, at least about 1 GPa, at least about 2 GPa, atleast about 5 GPa, at least about 10 GPa, at least about 20 GPa, atleast about 50 GPa, at least about 100 GPa, at least about 200 GPa, orat least about 400 GPa. In certain embodiments, the Young's elasticmodulus of the plurality of particles is less than or equal to about 500GPa, less than or equal to about 400 GPa, less than or equal to about200 GPa, less than or equal to about 100 GPa, less than or equal toabout 50 GPa, less than or equal to about 20 GPa, less than or equal toabout 10 GPa, less than or equal to about 5 GPa, less than or equal toabout 2 GPa, less than or equal to about 1 GPa, or less than or equal toabout 0.5 GPa. Combinations of the above-referenced ranges are alsopossible (e.g., between about 0.1 GPa and about 500 GPa). In aparticular embodiment, the Young′ elastic modulus of the particles is atleast about 1 Gpa. In certain embodiments, the Young's elastic modulusof the fused particles is substantially the same as the Young's elasticmodulus as the particles prior to fusion. The Young's elastic modulusmay be measured by nano-indentation (AFM).

In certain embodiments, the additional or second material (e.g., thepolymeric material such as a non-ionically conductive material) has aYoung's elastic modulus that is at least about 2 times, at least about 5times, at least about 10 times, at least about 20 times, at least about50 times, or at least about 100 times less than the Young's elasticmodulus of the particles (e.g., fused particles) used to form and/orpresent in the ion-conductive layer. The additional or second material(e.g., the polymeric material such as a non-ionically conductivematerial) may have a Young's elastic modulus that is less than or equalto about 100 times, less than or equal to about 50 times, less than orequal to about 10 times the Young's elastic modulus of the particles(e.g., fused particles) used to form and/or present in theion-conductive layer. Combinations of the above-referenced ranges arealso possible. Those skilled in the art would be capable of selectingsuitable methods for determining Young's elastic modulus of thematerials described herein.

In certain embodiments, the additional or second material (e.g., thepolymeric material such as a non-ionically conductive material) has ayield strength that is at least about 2, at least about 5, at leastabout 10, or at least about 100 times less than the yield strength ofthe particles (e.g., fused particles, and/or inorganic particles) usedto form and/or present in the ion-conductive layer. The additional orsecond material (e.g., the polymeric material such as a non-ionicallyconductive material) may have a yield strength that is less than orequal to about 100 times, less than or equal to about 50 times, lessthan or equal to about 10 times the yield strength of the particles(e.g., fused particles) used to form and/or present in theion-conductive layer. Combinations of the above-referenced ranges arealso possible. Those skilled in the art would be capable of selectingsuitable methods for determining yield strength of the materialsdescribed herein, including, for example, nanoindentation.

In some embodiments, the weight ratio of ionically conductive material(e.g., comprising the plurality of particles) and non-ionicallyconductive material (e.g., comprising a polymeric material) present inan ion-conductive layer is between about 80:20 and about 95:5, althoughother ranges are also possible. In some embodiments, the weight ratio ofionically conductive material and non-ionically conductive material isat least about 70:30, at least about 80:20, at least about 85:15, or atleast about 90:10. In some embodiments, the weight ratio of ionicallyconductive material and non-ionically conductive material is less thanor equal to about 95:5, less than or equal to about 90:10, or less thanor equal to about 85:15. Combinations of the above-referenced ranges arealso possible (e.g., between about 80:20 and about 95:5).

An ion-conductive layer comprising a plurality of particles (e.g., fusedparticles) may have any suitable thickness. In some embodiments, anion-conductive layer described herein may have an average thickness ofat least about 0.5 microns, at least about 1 micron, at least about 3microns, at least about 5 microns, at least about 10 microns, at leastabout 15 microns, or at least about 20 microns. In some embodiments, theaverage thickness of the ion-conductive layer is less than or equal toabout 25 microns, less than or equal to about 20 microns, less than orequal to about 10 microns, less than or equal to about 5 microns or lessthan or equal to about 3 microns. Other ranges are also possible.Combinations of the above-noted ranges are also possible (e.g., betweenabout 3 microns and about 25 microns, between about 5 microns and about10 microns). The average thickness of the ion-conductive layer can bedetermined, for example, using a drop gauge or scanning electronmicroscopy (SEM), as described above.

In some embodiments, the ion-conductive layer may be substantiallynon-porous (e.g., have a low porosity). For instance, in some cases, theplurality of particles are deposited on the first layer (optionally withan additional/second material) and form an ion-conductive layer that issubstantially non-porous. In some embodiments, less than or equal toabout 99.9%, less than or equal to about 99.5%, less than or equal toabout 99%, less than or equal to about 98%, or less than or equal toabout 97% of the ion-conductive layer is non-porous. In certainembodiments, at least about 95%, at least about 97%, at least about 98%,at least about 99%, or at least about 99.5% of the ion-conductive layeris non-porous. In certain embodiments, the ion-conductive layer has aparticular porosity. For example, the porosity of the ion-conductivelayer may be less than or equal to about 5%, less than or equal to about3%, less than or equal to about 2%, or less than or equal to about 1%.Porosity/non-porosity can be determined, for example, by mercuryporosimetry (e.g., Brunauer-Emmett-Teller porosity).

The ion-conductive layer may have any suitable density. In certainembodiments, the density of the ion-conductive layer is between about1.5 g/cm³ and about 6 g/cm³. For example, in some embodiments, theion-conductive layer has a density of at least about 1.5 g/cm³, at leastabout 2 g/cm³, at least about 2.5 g/cm³, at least about 3 g/cm³, atleast about 4 g/cm³, or at least about 5 g/cm³. In certain embodiments,the ion-conductive layer has a density of less than or equal to about 6g/cm³, less than or equal to about 5 g/cm³, less than or equal to about4 g/cm³, less than or equal to about 3 g/cm³, less than or equal toabout 2.5 g/cm³, or less than or equal to about 2 g/cm³. Combinations ofthe above-referenced ranges are also possible (e.g., between about 1.5g/cm³ and about 6 g/cm³). Other ranges are also possible.

In certain embodiments, the ion-conductive layer has an overall ionicconductivity (e.g., lithium ion conductivity) of at least about at leastabout 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, at least about 10⁻⁵ S/cm, atleast about 10⁻⁴ S/cm, or at least about 10⁻³ S/cm. In certainembodiments, the average ionic conductivity of the ion-conductive layer(e.g., lithium ion conductivity) may be less than or equal to about lessthan or equal to about 10⁻² S/cm, less than or equal to about 10⁻³ S/cm,less than or equal to about 10⁻⁴ S/cm, less than or equal to about 10⁻⁵S/cm, or less than or equal to about 10⁻⁶ S/cm. Combinations of theabove-referenced ranges are also possible (e.g., an average ionicconductivity of at least about 10⁻⁷ S/cm and less than or equal to about10⁻² S/cm, an average ionic conductivity of at least about 10⁻⁶ S/cm andless than or equal to about 10⁻² S/cm, an average ionic conductivity ofat least about 10⁻⁵ S/cm and less than or equal to about 10⁻³ S/cm).Conductivity (e.g., dry conductivity) may be measured at roomtemperature (e.g., 25 degrees Celsius), for example, using aconductivity bridge (i.e., an impedance measuring circuit) operating at1 kHz in the absence of an electrolyte and/or solvent (i.e., for a dryion-conductive layer).

In some embodiments, the percent difference in ionic conductivitybetween the particles (e.g., prior to deposition or fusing) and theresulting layer (e.g., comprising the particles), may be less than about1000%, less than about 700%, less than about 500%, less than about 200%,less than about 100%, less than about 50%, less than about 40%, lessthan about 30%, less than about 20%, less than about 10%, less thanabout 5%, less than about 3%, less than about 1%, or less than about0.5%. In some cases, the percent difference in ionic conductivitybetween the particles (e.g., prior to deposition or fusing) and theresulting layer (e.g., comprising the particles), may be greater than orequal to about 0.1%, greater than or equal to about 0.5%, greater thanor equal to about 1%, greater than or equal to about 3%, greater than orequal to about 5%, greater than or equal to about 10%, greater than orequal to about 20%, greater than or equal to about 50%, greater than orequal to about 100%, greater than or equal to about 200%, greater thanor equal to about 500%, greater than or equal to about 700%, or greaterthan or equal to about 1000%. Combinations of the above-referencedranges are also possible (e.g., between about 0.1% and about 10%). Insome embodiments, there is substantially no difference in ionicconductivity between the particles and the resulting layer. The percentdifferent may be calculated by subtracting the lower value of ionicconductivity from the higher value of ionic conductivity, and dividingby the higher value of ionic conductivity.

In some embodiments, the ion-conductive layer (e.g., comprising apolymer and a plurality of particles), as described herein, may have amean peak to valley roughness (R_(z)) of less than or equal to about 2μm, less than or equal to about 1.5 μm, less than or equal to about 1μm, less than or equal to about 0.9 μm, less than or equal to about 0.8μm, less than or equal to about 0.7 μm, less than or equal to about 0.6μm, less than or equal to about 0.5 μm, or any other appropriateroughness. In some embodiments, the ion-conductive layer has an R_(z) ofgreater than or equal to about 50 nm, greater than or equal to about 0.1μm, greater than or equal to about 0.2 μm, greater than or equal toabout 0.4 μm, greater than or equal to about 0.6 μm, greater than orequal to about 0.8 μm, greater than or equal to about 1 μm, or any otherappropriate roughness. Combinations of the above-noted ranges arepossible (e.g., an R_(z) of greater than or equal to about 0.1 μm andless than or equal to about 1 μm). Other ranges are also possible.

The mean peak to valley roughness (Rz) may be calculated, for example,by imaging the surface with a non-contact 3D optical microscope (e.g.,an optical profiler). Briefly, an image may be acquired at amagnification between about 5× and about 110× (e.g., an area of betweenabout 50 microns×50 microns and about 1.2 mm×1.2 mm) depending on theoverall surface roughness. Those skilled in the art would be capable ofselecting an appropriate magnification for imaging the sample. The meanpeak to valley roughness can be determined by taking an average of theheight difference between the highest peaks and the lowest valleys for agiven sample size (e.g., averaging the height difference between thefive highest peaks and the five lowest valleys across the imaged area ofthe sample) at several different locations on the sample (e.g., imagesacquired at five different areas on the sample).

In some embodiments, the first layer on which the ion-conductive layer(e.g., an electroactive layer), may have a mean peak to valley roughnessin one or more of the above-referenced ranges for the ion-conductivelayer. In some cases, the roughness may be caused at least in part byparticles being embedded in the first layer.

As described herein, it may be desirable to determine if anion-conductive layer (e.g., comprising a plurality of fused particles)has advantageous properties as compared to other materials used as aprotective layer (e.g., a protective layer formed of a polymericmaterial alone, a protective layer formed of an ion-conductive materialalone, or combinations thereof) for particular electrochemical systems.Therefore, simple screening tests can be employed to help select betweencandidate materials. One simple screening test includes positioning anion-conductive layer (e.g., comprising a plurality of fused particles)in an electrochemical cell, e.g., as a protective layer in a cell. Theelectrochemical cell may then undergo multiple discharge/charge cycles,and the electrochemical cell may be observed for whether inhibitory orother destructive behavior occurs compared to that in a control system.If inhibitory or other destructive behavior is observed during cyclingof the cell, as compared to the control system, it may be indicative ofa degradation mechanisms of the ion-conductive layer, within theassembled electrochemical cell. Using the same electrochemical cell itis also possible to evaluate the electrical conductivity and ionconductivity of the ion-conductive layer using methods known to one ofordinary skill in the art. The measured values may be compared to selectbetween candidate materials and may be used for comparison with baselinematerial(s) in the control.

In some embodiments, it may be desirable to test the ion-conductivelayer for swelling in the presence of a particular electrolyte orsolvent to be used in an electrochemical cell (including any salts oradditives present). A simple screening test may involve, for example,pieces of the ion-conductive layer that are weighed and then placed in asolvent or an electrolyte to be used in an electrochemical cell for anysuitable amount of time (e.g., 24 hours). The percent difference inweight (or volume) of the ion-conductive layer before and after theaddition of a solvent or an electrolyte may determine the amount ofswelling of the ion-conductive layer in the presence of the electrolyteor the solvent.

Another simple screen test involves determining the stability (i.e.,integrity) of an ion-conductive layer to polysulfides (e.g., for use ina lithium-sulfur electrochemical cells) and/or an electrolyte (e.g., foruse in lithium-ion electrochemical cells). Briefly, the ion-conductivelayer may be exposed to a polysulfide solution/mixture or liquidelectrolyte for any suitable amount of time (e.g., 72 hours) and thepercent weight loss of the ion-conductive layer after exposure to thepolysulfide solution or liquid electrolyte may be determined bycalculating the difference in weight of the ion-conductive layer beforeand after the exposure. For example, in some embodiments, the percentweight loss of the ion-conductive layer after exposure to thepolysulfide solution or liquid electrolyte may be less than or equal toabout 15 wt %, less than or equal to about 10 wt %, less than or equalto about 5 wt %, less than or equal to about 2 wt %, less than or equalto about 1 wt %, or less than or equal to about 0.5 wt %. In certainembodiments, the percent weight loss of the ion-conductive layer afterexposure to the polysulfide solution or liquid electrolyte may begreater than about 0.1 wt %, greater than about 0.5 wt %, greater thanabout 1 wt %, greater than about 2 wt %, greater than about 5 wt %, orgreater than about 10 wt %. Combinations of the above-referenced rangesare also possible (e.g., between about 0.1 wt % and about 5 wt %). Insome cases, x-ray diffraction may be used to determine stability of anion-conductive layer to polysulfides or liquid electrolytes.

The above described screening tests may also be adapted and used todetermine the properties of individual components of the ion-conductivelayer (e.g. polymeric material/polymer layer and/or a plurality ofparticles).

While many embodiments described herein relate to lithium-sulfur and/orlithium-ion electrochemical cells, it is to be understood that anyanalogous alkali metal/sulfur electrochemical cells (including alkalimetal anodes) can be used. As noted above and as described in moredetail herein, in some embodiments, the ion-conductive layer isincorporated into an electrochemical cell as a protective layer for anelectrode. In some embodiments, the ion-conductive layers disclosedherein may include in an electrochemical cell comprising at least oneelectrode structure. In some cases, the electrochemical cell may befabricated by providing an electrode structure, one or more theion-conductive layers, and an electrolyte layer. The electrodestructures may include an electroactive layer (e.g., an anode or acathode) and one or more ion-conductive layers. The ion-conductivelayers may be highly conductive to electroactive material ions and mayprotect the underlying electroactive material surface from reaction withcomponents in the electrolyte, as described above. In some embodiments,the ion-conductive layer may be adjacent the anode. In some embodiments,the ion-conductive layer may be adjacent the cathode. In certainembodiments, the ion-conductive layer may be adjacent a separator.

An electrochemical cell or an article for use in an electrochemical cellmay include an electroactive material layer. In some embodiments, afirst layer described herein (e.g., a layer on which an ion-conductivelayer is formed) comprises an electroactive material (e.g., the firstlayer is an electroactive layer). In some cases, the first layer may bean anode (e.g., an anode of an electrochemical cell).

Suitable electroactive materials for use as anode active materials inthe electrochemical cells described herein include, but are not limitedto, lithium metal such as lithium foil and lithium deposited onto aconductive substrate, and lithium alloys (e.g., lithium-aluminum alloysand lithium-tin alloys). Lithium can be contained as one film or asseveral films, optionally separated by a protective material such as aceramic material or an ion conductive material described herein.Suitable ceramic materials include silica, alumina, or lithiumcontaining glassy materials such as lithium phosphates, lithiumaluminates, lithium silicates, lithium phosphorous oxynitrides, lithiumtantalum oxide, lithium aluminosulfides, lithium titanium oxides,lithium silcosulfides, lithium germanosulfides, lithium aluminosulfides,lithium borosulfides, and lithium phosphosulfides, and combinations oftwo or more of the preceding. Suitable lithium alloys for use in theembodiments described herein can include alloys of lithium and aluminum,magnesium, silicium (silicon), indium, and/or tin. While these materialsmay be preferred in some embodiments, other cell chemistries are alsocontemplated. In some embodiments, the anode may comprise one or morebinder materials (e.g., polymers, etc.).

One or more electroactive layers (e.g., comprising an electroactivematerial), as described herein, may have a mean peak to valley roughness(R_(z)) of less than or equal to about 10 μm, less than or equal toabout 2 μm, less than or equal to about 1.5 μm, less than or equal toabout 1 μm, less than or equal to about 0.9 μm, less than or equal toabout 0.8 μm, less than or equal to about 0.7 μm, less than or equal toabout 0.6 μm, less than or equal to about 0.5 μm, or any otherappropriate roughness. In some embodiments, the one or moreelectroactive layers (e.g., comprising an electroactive material) has anR_(z) of greater than or equal to about 50 nm, greater than or equal toabout 0.1 μm, greater than or equal to about 0.2 μm, greater than orequal to about 0.4 μm, greater than or equal to about 0.6 μm, greaterthan or equal to about 0.8 μm, greater than or equal to about 1 μm,greater than or equal to about 2 μm, greater than or equal to about 5μm, or any other appropriate roughness. Combinations of the above-notedranges are possible (e.g., an R_(z) of greater than or equal to about0.1 μm and less than or equal to about 1 μm). Other ranges are alsopossible. In some embodiments, the mean peak to valley roughness of oneor more electroactive layers is determined prior to charge/discharge ofthe electrochemical cell. The mean peak to valley roughness (R_(z)) ofthe one or more electroactive layers may be determined, for example, byimaging the surface with a non-contact 3D optical microscope (e.g., anoptical profiler), as described above.

In some such embodiments, a first layer described herein (e.g., a layeron which an ion-conductive layer is formed) may be a cathode (e.g., acathode of an electrochemical cell). Suitable electroactive materialsfor use as cathode active materials in the cathode of theelectrochemical cells described herein may include, but are not limitedto, electroactive transition metal chalcogenides, electroactiveconductive polymers, sulfur, carbon, and/or combinations thereof. Asused herein, the term “chalcogenides” pertains to compounds that containone or more of the elements of oxygen, sulfur, and selenium. Examples ofsuitable transition metal chalcogenides include, but are not limited to,the electroactive oxides, sulfides, and selenides of transition metalsselected from the group consisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y,Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, and Ir. In oneembodiment, the transition metal chalcogenide is selected from the groupconsisting of the electroactive oxides of nickel, manganese, cobalt, andvanadium, and the electroactive sulfides of iron. In certainembodiments, the cathode may include as an electroactive specieselemental sulfur, sulfides, and/or polysulfides. In other embodiments,an intercalation electrode (e.g., a lithium-intercalation cathode) maybe used. Non-limiting examples of suitable materials that mayintercalate ions of an electroactive material (e.g., alkaline metalions) include oxides, titanium sulfide, and iron sulfide. Additionalexamples include LixCoO₂, Li_(x)NiO₂, LixMnO₂, LixMn₂O₄, Li_(x)FePO₄,Li_(x)CoPO₄, Li_(x)MnPO₄, and Li_(x)NiPO₄, where (0<x≦1), andLiNi_(x)Mn_(y)Co_(z)O₂ where (x+y+z=1).

In one embodiment, a cathode includes one or more of the followingmaterials: manganese dioxide, iodine, silver chromate, silver oxide andvanadium pentoxide, copper oxide, copper oxyphosphate, lead sulfide,copper sulfide, iron sulfide, lead bismuthate, bismuth trioxide, cobaltdioxide, copper chloride, manganese dioxide, and carbon. In anotherembodiment, the cathode active layer comprises an electroactiveconductive polymer. Examples of suitable electroactive conductivepolymers include, but are not limited to, electroactive andelectronically conductive polymers selected from the group consisting ofpolypyrroles, polyanilines, polyphenylenes, polythiophenes, andpolyacetylenes. Examples of conductive polymers include polypyrroles,polyanilines, and polyacetylenes.

In some embodiments, electroactive materials for use as cathode activematerials in electrochemical cells described herein includeelectroactive sulfur-containing materials (e.g., lithium-sulfurelectrochemical cells). “Electroactive sulfur-containing materials,” asused herein, relates to cathode active materials which comprise theelement sulfur in any form, wherein the electrochemical activityinvolves the oxidation or reduction of sulfur atoms or moieties. Thenature of the electroactive sulfur-containing materials useful in thepractice of this invention may vary widely, as known in the art. Forexample, in one embodiment, the electroactive sulfur-containing materialcomprises elemental sulfur. In another embodiment, the electroactivesulfur-containing material comprises a mixture of elemental sulfur and asulfur-containing polymer. Thus, suitable electroactivesulfur-containing materials may include, but are not limited to,elemental sulfur and organic materials comprising sulfur atoms andcarbon atoms, which may or may not be polymeric. Suitable organicmaterials include those further comprising heteroatoms, conductivepolymer segments, composites, and conductive polymers.

In certain embodiments, the sulfur-containing material (e.g., in anoxidized form) comprises a polysulfide moiety, Sm, selected from thegroup consisting of covalent Sm moieties, ionic Sm moieties, and ionicSm₂— moieties, wherein m is an integer equal to or greater than 3. Insome embodiments, m of the polysulfide moiety Sm of thesulfur-containing polymer is an integer equal to or greater than 6 or aninteger equal to or greater than 8. In some cases, the sulfur-containingmaterial may be a sulfur-containing polymer. In some embodiments, thesulfur-containing polymer has a polymer backbone chain and thepolysulfide moiety Sm is covalently bonded by one or both of itsterminal sulfur atoms as a side group to the polymer backbone chain. Incertain embodiments, the sulfur-containing polymer has a polymerbackbone chain and the polysulfide moiety Sm is incorporated into thepolymer backbone chain by covalent bonding of the terminal sulfur atomsof the polysulfide moiety.

In some embodiments, the electroactive sulfur-containing materialcomprises more than 50% by weight of sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises more than 75% byweight of sulfur (e.g., more than 90% by weight of sulfur).

As will be known by those skilled in the art, the nature of theelectroactive sulfur-containing materials described herein may varywidely. In some embodiments, the electroactive sulfur-containingmaterial comprises elemental sulfur. In certain embodiments, theelectroactive sulfur-containing material comprises a mixture ofelemental sulfur and a sulfur-containing polymer.

In certain embodiments, an electrochemical cell as described herein,comprises one or more cathodes comprising sulfur as a cathode activespecies. In some such embodiments, the cathode includes elemental sulfuras a cathode active species.

In some embodiments, a first layer described herein (e.g., a layer onwhich an ion-conductive layer is formed) is a separator. For instance,in some embodiments, the plurality of particles are deposited on aseparator (e.g., via aerosol deposition). Such separators generallycomprise a polymeric material (e.g., polymeric material that does ordoes not swell upon exposure to electrolyte). In some embodiments, theseparator is located between the ion-conductive layer and an electrode(e.g., an anode, a cathode).

The separator can be configured to inhibit (e.g., prevent) physicalcontact between a first electrode and a second electrode, which couldresult in short circuiting of the electrochemical cell. The separatorcan be configured to be substantially electronically non-conductive,which can inhibit the degree to which the separator causes shortcircuiting of the electrochemical cell. In certain embodiments, all orportions of the separator can be formed of a material with a bulkelectronic resistivity of at least about 10⁴, at least about 10⁵, atleast about 10¹⁰, at least about 10¹⁵, or at least about 10²⁰Ohm-meters. Bulk electronic resistivity may be measured at roomtemperature (e.g., 25 degrees Celsius).

In some embodiments, the separator can be ionically conductive, while inother embodiments, the separator is substantially ionicallynon-conductive. In some embodiments, the average ionic conductivity ofthe separator is at least about 10⁻⁷ S/cm, at least about 10⁻⁶ S/cm, atleast about 10⁻⁵ S/cm, at least about 10⁻⁴ S/cm, at least about 10⁻²S/cm, at least about 10⁻¹ S/cm. In certain embodiments, the averageionic conductivity of the separator may be less than or equal to about 1S/cm, less than or equal to about 10⁻¹ S/cm, less than or equal to about10⁻² S/cm, less than or equal to about 10⁻³ S/cm, less than or equal toabout 10⁻⁴ S/cm, less than or equal to about 10⁻⁵ S/cm, less than orequal to about 10⁻⁶ S/cm, less than or equal to about 10⁻⁷ S/cm, or lessthan or equal to about 10⁻⁸ S/cm. Combinations of the above-referencedranges are also possible (e.g., an average ionic conductivity of atleast about 10⁻⁸ S/cm and less than or equal to about 10⁻¹ S/cm).

In some embodiments, the separator can be a solid. The separator may beporous to allow an electrolyte solvent to pass through it. In somecases, the separator does not substantially include a solvent (like in agel), except for solvent that may pass through or reside in the pores ofthe separator. In other embodiments, a separator may be in the form of agel.

A separator as described herein can be made of a variety of materials.The separator may be polymeric in some instances, or formed of aninorganic material (e.g., glass fiber filter papers) in other instances.Examples of suitable separator materials include, but are not limitedto, polyolefins (e.g., polyethylenes, poly(butene-1), poly(n-pentene-2),polypropylene, polytetrafluoroethylene), polyamines (e.g., poly(ethyleneimine) and polypropylene imine (PPI)); polyamides (e.g., polyamide(Nylon), poly(ε-caprolactam) (Nylon 6), poly(hexamethylene adipamide)(Nylon 66)), polyimides (e.g., polyimide, polynitrile, andpoly(pyromellitimide-1,4-diphenyl ether) (Kapton®) (NOMEX®) (KEVLAR®));polyether ether ketone (PEEK); vinyl polymers (e.g., polyacrylamide,poly(2-vinyl pyridine), poly(N-vinylpyrrolidone),poly(methylcyanoacrylate), poly(ethylcyanoacrylate),poly(butylcyanoacrylate), poly(isobutylcyanoacrylate), poly(vinylacetate), poly (vinyl alcohol), poly(vinyl chloride), poly(vinylfluoride), poly(2-vinyl pyridine), vinyl polymer, polychlorotrifluoroethylene, and poly(isohexylcynaoacrylate)); polyacetals; polyesters(e.g., polycarbonate, polybutylene terephthalate, polyhydroxybutyrate);polyethers (poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO),poly(tetramethylene oxide) (PTMO)); vinylidene polymers (e.g.,polyisobutylene, poly(methyl styrene), poly(methylmethacrylate) (PMMA),poly(vinylidene chloride), and poly(vinylidene fluoride)); polyaramides(e.g., poly(imino-1,3-phenylene iminoisophthaloyl) andpoly(imino-1,4-phenylene iminoterephthaloyl)); polyheteroaromaticcompounds (e.g., polybenzimidazole (PBI), polybenzobisoxazole (PBO) andpolybenzobisthiazole (PBT)); polyheterocyclic compounds (e.g.,polypyrrole); polyurethanes; phenolic polymers (e.g.,phenol-formaldehyde); polyalkynes (e.g., polyacetylene); polydienes(e.g., 1,2-polybutadiene, cis or trans-1,4-polybutadiene); polysiloxanes(e.g., poly(dimethylsiloxane) (PDMS), poly(diethylsiloxane) (PDES),polydiphenylsiloxane (PDPS), and polymethylphenylsiloxane (PMPS)); andinorganic polymers (e.g., polyphosphazene, polyphosphonate, polysilanes,polysilazanes). In some embodiments, the polymer may be selected frompoly(n-pentene-2), polypropylene, polytetrafluoroethylene, polyamides(e.g., polyamide (Nylon), poly(e-caprolactam) (Nylon 6),poly(hexamethylene adipamide) (Nylon 66)), polyimides (e.g.,polynitrile, and poly(pyromellitimide-1,4-diphenyl ether) (Kapton®)(NOMEX®) (KEVLAR®)), polyether ether ketone (PEEK), and combinationsthereof.

The mechanical and electronic properties (e.g., conductivity,resistivity) of these polymers are known. Accordingly, those of ordinaryskill in the art can choose suitable materials based on their mechanicaland/or electronic properties (e.g., ionic and/or electronicconductivity/resistivity), and/or can modify such polymers to beionically conducting (e.g., conductive towards single ions) based onknowledge in the art, in combination with the description herein. Forexample, the polymer materials listed above and herein may furthercomprise salts, for example, lithium salts (e.g., LiSCN, LiBr, LiI,LiClO₄, LiAsF₆, LiSO₃CF₃, LiSO₃CH₃, LiBF₄, LiB(Ph)₄, LiPF₆,LiC(SO₂CF₃)₃, and LiN(SO₂CF₃)₂), to enhance ionic conductivity, ifdesired.

Those of ordinary skill in the art, given the present disclosure, wouldbe capable of selecting appropriate materials for use as the separator.Relevant factors that might be considered when making such selectionsinclude the ionic conductivity of the separator material; the ability todeposit or otherwise form the separator material on or with othermaterials in the electrochemical cell; the flexibility of the separatormaterial; the porosity of the separator material (e.g., overallporosity, average pore size, pore size distribution, and/or tortuosity);the compatibility of the separator material with the fabrication processused to form the electrochemical cell; the compatibility of theseparator material with the electrolyte of the electrochemical cell;and/or the ability to adhere the separator material to the ion conductormaterial. In certain embodiments, the separator material can be selectedbased on its ability to survive the aerosol deposition processes withoutmechanically failing. For example, in embodiments in which relativelyhigh velocities are used to deposited the plurality of particles (e.g.,inorganic particles), the separator material can be selected orconfigured to withstand such deposition.

The first layer (e.g., the separator) may be porous. In someembodiments, the separator pore size may be, for example, less than 5microns. In certain embodiments, the separator pore size may be between50 nm and 5 microns, between 50 nm and 500 nm, between 100 nm and 300nm, between 300 nm and 1 micron, between 500 nm and 5 microns. In someembodiments, the pore size may be less than or equal to 5 microns, lessthan or equal to 1 micron, less than or equal to 500 nm, less than orequal to 300 nm, less than or equal to 100 nm, or less than or equal to50 nm. In some embodiments, the pore size may be greater than 50 nm,greater than 100 nm, greater than 300 nm, greater than 500 nm, orgreater than 1 micron. Other values are also possible. Combinations ofthe above-noted ranges are also possible (e.g., a pore size of less than300 nm and greater than 100 nm). In certain embodiments, the separatormay be substantially non-porous.

As described herein, in certain embodiments, the electrochemical cellcomprises an electrolyte. The electrolytes used in electrochemical orbattery cells can function as a medium for the storage and transport ofions, and in the special case of solid electrolytes and gelelectrolytes, these materials may additionally function as a separatorbetween the anode and the cathode. Any suitable liquid, solid, or gelmaterial capable of storing and transporting ions may be used, so longas the material facilitates the transport of ions (e.g., lithium ions)between the anode and the cathode. The electrolyte is electronicallynon-conductive to prevent short circuiting between the anode and thecathode. In some embodiments, the electrolyte may comprise a non-solidelectrolyte.

In some embodiments, an electrolyte is in the form of a layer having aparticular thickness. An electrolyte layer may have a thickness of, forexample, at least 1 micron, at least 5 microns, at least 10 microns, atleast 15 microns, at least 20 microns, at least 25 microns, at least 30microns, at least 40 microns, at least 50 microns, at least 70 microns,at least 100 microns, at least 200 microns, at least 500 microns, or atleast 1 mm. In some embodiments, the thickness of the electrolyte layeris less than or equal to 1 mm, less than or equal to 500 microns, lessthan or equal to 200 microns, less than or equal to 100 microns, lessthan or equal to 70 microns, less than or equal to 50 microns, less thanor equal to 40 microns, less than or equal to 30 microns, less than orequal to 20 microns, less than or equal to 10 microns, or less than orequal to 50 microns. Other values are also possible. Combinations of theabove-noted ranges are also possible.

In some embodiments, the electrolyte includes a non-aqueous electrolyte.Suitable non-aqueous electrolytes may include organic electrolytes suchas liquid electrolytes, gel polymer electrolytes, and solid polymerelectrolytes. These electrolytes may optionally include one or moreionic electrolyte salts (e.g., to provide or enhance ionic conductivity)as described herein. Examples of useful non-aqueous liquid electrolytesolvents include, but are not limited to, non-aqueous organic solvents,such as, for example, N-methyl acetamide, acetonitrile, acetals, ketals,esters, carbonates, sulfones, sulfites, sulfolanes, aliphatic ethers,acyclic ethers, cyclic ethers, glymes, polyethers, phosphate esters,siloxanes, dioxolanes, N-alkylpyrrolidones, substituted forms of theforegoing, and blends thereof. Examples of acyclic ethers that may beused include, but are not limited to, diethyl ether, dipropyl ether,dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane,diethoxyethane, 1,2-dimethoxypropane, and 1,3-dimethoxypropane. Examplesof cyclic ethers that may be used include, but are not limited to,tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran, 1,4-dioxane,1,3-dioxolane, and trioxane. Examples of polyethers that may be usedinclude, but are not limited to, diethylene glycol dimethyl ether(diglyme), triethylene glycol dimethyl ether (triglyme), tetraethyleneglycol dimethyl ether (tetraglyme), higher glymes, ethylene glycoldivinyl ether, diethylene glycol divinyl ether, triethylene glycoldivinyl ether, dipropylene glycol dimethyl ether, and butylene glycolethers. Examples of sulfones that may be used include, but are notlimited to, sulfolane, 3-methyl sulfolane, and 3-sulfolene. Fluorinatedderivatives of the foregoing are also useful as liquid electrolytesolvents.

In some cases, mixtures of the solvents described herein may also beused. For example, in some embodiments, mixtures of solvents areselected from the group consisting of 1,3-dioxolane and dimethoxyethane,1,3-dioxolane and diethyleneglycol dimethyl ether, 1,3-dioxolane andtriethyleneglycol dimethyl ether, and 1,3-dioxolane and sulfolane. Theweight ratio of the two solvents in the mixtures may range, in somecases, from about 5 wt %:95 wt % to 95 wt %:5 wt %.

Non-limiting examples of suitable gel polymer electrolytes includepolyethylene oxides, polypropylene oxides, polyacrylonitriles,polysiloxanes, polyimides, polyphosphazenes, polyethers, sulfonatedpolyimides, perfluorinated membranes (NAFION resins), polydivinylpolyethylene glycols, polyethylene glycol diacrylates, polyethyleneglycol dimethacrylates, derivatives of the foregoing, copolymers of theforegoing, cross-linked and network structures of the foregoing, andblends of the foregoing.

Non-limiting examples of suitable solid polymer electrolytes includepolyethers, polyethylene oxides, polypropylene oxides, polyimides,polyphosphazenes, polyacrylonitriles, polysiloxanes, derivatives of theforegoing, copolymers of the foregoing, cross-linked and networkstructures of the foregoing, and blends of the foregoing.

In some embodiments, the non-aqueous electrolyte comprises at least onelithium salt. For example, in some cases, the at least one lithium saltis selected from the group consisting of LiNO₃, LiPF₆, LiBF₄, LiClO₄,LiAsF₆, Li₂SiF₆, LiSbF₆, LiAlCl₄, lithium bis-oxalatoborate, LiCF₃SO₃,LiN(SO₂F)₂, LiC(C_(n)F_(2n+1)SO₂)₃, wherein n is an integer in the rangeof from 1 to 20, and (C_(n)F_(2n+1)SO₂)_(m)XLi with n being an integerin the range of from 1 to 20, m being 1 when X is selected from oxygenor sulfur, m being 2 when X is selected from nitrogen or phosphorus, andm being 3 when X is selected from carbon or silicon.

In some embodiments, the first layer described herein (e.g., a layer onwhich an ion-conductive layer is formed) comprises a material that candissolve in an electrolyte to be used with the electrochemical cell, orin any other suitable solvent (e.g., a non-electrolyte solvent).Accordingly, at least a portion, or all, of the first layer may beremoved from the ion-conductive layer. Removal of at least a portion, orall, of the first layer may take place prior to the ion-conductive layerbeing placed in an electrochemical cell, or after the ion-conductivelayer being placed in an electrochemical cell. In some cases, removalcan take place during cycling of the electrochemical cell. Non-limitingexamples of materials that can dissolve in an electrolyte or any othersuitable solvent include, for example, polysulphone, polyethylene oxide,kynar, and polystyrene. For example, in some embodiments, at least about10 vol %, at least about 20 vol %, at least about 30 vol %, at leastabout 50 vol %, at least about 70 vol %, or at least about 90 vol % ofthe first layer may be removed from the ion-conductive layer. In certainembodiments, less than or equal to about 100 vol %, less than or equalto about 90 vol %, less than or equal to about 70 vol %, less than orequal to about 50 vol %, less than or equal to about 30 vol %, or lessthan or equal to about 20 vol % of the first layer may be removed fromthe ion-conductive layer. Combinations of the above-referenced rangesare also possible (e.g., between about 10 vol % and about 100 vol %). Insome cases, substantially all (e.g., 100%) of the first layer may beremoved from the ion-conductive layer.

In some embodiments, an electrode structure described herein comprisesat least one current collector. Materials for the current collector maybe selected, in some cases, from metals (e.g., copper, nickel, aluminum,passivated metals, and other appropriate metals), metallized polymers,electrically conductive polymers, polymers comprising conductiveparticles dispersed therein, and other appropriate materials. In certainembodiments, the current collector is deposited onto the electrode layerusing physical vapor deposition, chemical vapor deposition,electrochemical deposition, sputtering, doctor blading, flashevaporation, or any other appropriate deposition technique for theselected material. In some cases, the current collector may be formedseparately and bonded to the electrode structure. It should beappreciated, however, that in some embodiments a current collectorseparate from the electroactive layer may not be needed.

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

EXAMPLES Example 1

This example illustrates the formation of an ion-conductive layer bydepositing and fusing a plurality of particles by aerosol deposition ona substrate.

Anionically-conductive solid particles of LiSiPS were prepared with aparticle distribution with an average of about 10 microns. Particleswere prepared by mixing Li₂S, SiS₂ and P₂S₅ and heating the componentsto about 700° C. After cooling, the material was ground and partiallywet milled (e.g., in dry hexane/a water-free non-reactive organicsolvent such as a dried alkane) in order to achieve the desired particlesize distribution. Sieving was also conducted, in some cases, to removelarger particles (e.g., particles having a diameter of greater than >25micrometer) from the distribution. The particles were loaded into anaerosol deposition method (ADM) powder feed system, and using a carriergas pressure of 90 PSI, the particles were sprayed onto a 4 micron-thickPET substrate in a rough vacuum environment (0.5 mTorr). Via a motioncontrol system both the substrate holder and the aerosol nozzle may bemoved to yield the desired ceramic coverage on the substrate. SEM imagesof the final coating are shown in FIGS. 3A-3B. As can be seen from theimages, the resulting coating was dense and about 27 microns to about 34microns in thickness. A portion of the coating (above the 27 μmcross-section in FIG. 3B) was broken off during handling, and as such,the thickness of the measured portion of the coating is less than thatshown in FIG. 3A.

FIGS. 3C-3D are top-down views of the LiSPS material deposited on thePET substrate. Fused areas can be seen in the magnified view in FIG. 3D,including smaller particles on the surface.

Example 2

This example illustrates the formation of another ion-conductive layerby depositing and fusing a plurality of particles by aerosol depositionon a substrate.

SEM cross-section images of Garnet particles deposited on a 4 micronthickness PET substrate via aerosol deposition are shown in FIGS. 4A-4B.The deposition process as described in Example 1 was followed except acarrier gas pressure of 100 PSI and a pressure of 1 Torr was used. FIG.4A shows a fused, crystalline portion 210 having a thickness ofapproximately 3.8 μm. A top portion 220 included some fused particles,but this portion was less fused that portion 210. The entire thicknessof the layer was 4.9 μm (FIG. 4B).

Comparative Example 2

This comparative example illustrates the formation of the ion-conductivelayer in Example 2 with partial fusion of the plurality of particles.

An SEM cross-section image of Garnet particles deposited on a 4 micronthickness PET substrate via aerosol deposition, as described in Example2, is shown in

FIG. 4C. FIG. 4C shows a fused, crystalline portion 250 and a partiallyfused portion 260. The deposition process as described in Example 1 wasfollowed except a carrier gas pressure of 80 PSI and a pressure of 1Torr was used.

Example 3

This example illustrates the formation of yet another ion-conductivelayer by depositing and fusing a plurality of particles by aerosoldeposition on a substrate.

Top-down views of an oxy-sulfide ceramic particles deposited via aerosoldeposition on a 25 micron thickness coating of lithium on copper foilare shown in FIGS. 5A-5C. The deposition process as described in Example1 was followed except a carrier gas pressure of 30 PSI and a pressure of1 Torr was used. Although the ceramic coating seems to have adopted asurface roughness similar, or larger, than that of the original lithiumsurface, the coating itself is continuous across the thickness of thelayer.

FIG. 5D is an SEM cross-section image of the ion-conductive layercomprising fused oxy-sulfide ceramic particles deposited via aerosoldeposition on the 25 micron thickness coating of lithium on copper foil.

Comparative Example 3

This comparative example illustrates the formation of the ion-conductivelayer in Example 3 with poor fusion of the plurality of particles.

Oxy-sulfide ceramic particles were deposited via aerosol deposition on a25 micron thickness coating of lithium on copper foil. The depositionprocess as described in Example 1 was followed except a carrier gaspressure of 15 PSI and a pressure of 1 Torr was used. However, theoxy-sulfide ceramic particles were deposited such that the particles didnot fuse or fused partially (poor fusion). FIGS. 6A-6B are SEMcross-section images of an ion-conductive layer comprising at least aportion of unfused particles 310 and partially fused oxy-sulfide ceramicparticle region 320.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is: 1-65. (canceled)
 66. A method of forming an articlefor use in an electrochemical cell, the method comprising: exposing afirst layer comprising a first material to a plurality of particleshaving a velocity of at least 200 m/s, wherein the particles comprise asecond material different from the first material; embedding at least aportion of the particles in the first layer; and forming a second layercomprising the second material, wherein the second layer has an ionicconductivity between about 10⁻⁶ S/cm and about 10⁻² S/cm.
 67. A methodof forming an article for use in an electrochemical cell, the methodcomprising: exposing a first layer comprising a first material to aplurality of particles having a velocity sufficient to cause fusion ofat least some of the particles, wherein the particles comprise a secondmaterial; embedding at least a portion of the particles in the firstlayer; and forming a second layer comprising the second material,wherein the second layer has an ionic conductivity between about 10⁻⁶S/cm and about 10⁻² S/cm.
 68. A method of claim 67, comprising fusing atleast a portion of the plurality of particles.
 69. A method of claim 67,comprising forming a continuous, ionically conductive pathway from theplurality of particles.
 70. A method of claim 67, wherein exposing thefirst layer to the plurality of particles comprises spraying theplurality of particles onto the first layer using aerosol deposition.71. A method of claim 67, wherein the exposing step is performed at apressure of at least 10 mTorr.
 72. A method of claim 67, wherein theexposing step is performed at a temperature of less than 500° C.
 73. Amethod of claim 67, comprising exposing the first layer comprising tothe plurality of particles having a velocity of at least 500 m/s, and upto 2000 m/s.
 74. A method of claim 67, wherein at least 10 vol % of thesecond layer comprises one or more continuous pathways.
 75. A method ofclaim 67, wherein the second layer has an ionic conductivity betweenabout 10⁻⁵ S/cm and about 10⁻³ S/cm.
 76. A method of claim 67, whereinthe second layer has an average thickness between about 3 microns andabout 25 microns.
 77. A method of claim 67, wherein the plurality ofparticles have an average largest cross-sectional dimension of betweenabout 0.5 microns and about 20 microns.
 78. A method of claim 67 whereinat least 50% of the plurality of particles are fused to one another. 79.(canceled)
 80. A method of claim 67, wherein the second layer comprisesan ionically-conductive material and a non-ionically conductivematerial.
 81. A method of claim 67, wherein the second layer comprisesan ionically-conductive material and a non-ionically conductivematerial, and wherein a weight ratio of the ionically conductivematerial to the non-ionically conductive material is at least 80:20. 82.A method of claim 67, wherein the ionically conductive materialcomprises an inorganic material.
 83. A method of claim 67, wherein theionically-conductive material comprises a ceramic; optionally, whereinthe ceramic is a garnet.
 84. (canceled)
 85. A method of claim 67,wherein the ionically conductive material is between 1% and 99%crystalline.
 86. A method of claim 67, wherein the ionically conductivematerial has a Young's elastic modulus of at least 1 GPa.
 87. A methodof claim 67, wherein the second layer comprises an ionically-conductivematerial and a non-ionically conductive material, and wherein thenon-ionically conductive material has a Young's elastic modulus of atleast 2 times smaller than the modulus of ionically conductive material.88. A method of claim 80, wherein the non-ionically conductive materialcomprises a polymer.
 89. A method of claim 80, wherein the non-ionicallyconductive material comprises an inorganic material.
 90. A method ofclaim 67, wherein the second layer has a density of between 1.5 and 6g/cm³.
 91. A method of claim 67, wherein the second layer has a porosityof less than about 5%. 92-94. (canceled)
 95. A method of claim 67,wherein the first layer comprises a polymer.
 96. A method of claim 95,wherein the polymer is a polymer gel or forms polymer gel when exposedto liquid electrolyte.
 97. (canceled)
 98. A method of claim 67, whereinthe first layer comprises lithium metal.
 99. A method of claim 67,wherein the first layer is a separator.
 100. A method of claim 67,wherein the first layer is porous.
 101. A method of claim 67, whereinthe first layer is non-porous. 102-103. (canceled)